Windows disk Clean up systems

Disk Cleanup: deleting unnecessary files
To free some space on your hard disk for better purposes, you have to do a disk cleanup. With the Disk Cleanup utility (Start Menu, All Programs, Accessories, System tools) you have a build in tool to remove many unnecessary files from your hard disk. Select the C: drive and on the first tab check all items to delete.
However, the cleaning is not thorough, especially the 'temporary (internet) files' folders (used files from the last few days will not be cleaned)! It is better to clean them yourself as well, as shown below. Most files are system files and/or hidden, so make sure you can see those type of files in the Windows Explorer (Tools, Folder Options, tab View, enable Display the content of system folders, enable Show hidden files and folders, disable Hide extensions for known file types and disable Hide protected operating system files).
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DELETE INDEX.DAT FILES MANUALLY
Disk Cleanup doesn't always work correctly, especially when the index.dat file is corrupt. Another reason to delete the files manually in the Windows Explorer.
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C:\HIBERFIL.SYS (hidden, as big as the main memory)
This file is created by the hibernation option (Control Panel, Power Options, tab Hibernate). With this option you are able to hibernate your computer. When your computer hibernates, it stores the main memory into the hiberfil.sys file on your C: partition before it shuts down. When you turn on the computer, it returns to its previous state by reloading the main memory with the information in the hiberfil.sys. To turn off this heavy disk consuming option, disable the Enable hibernation option on this tab.
C:\System Volume Information (hidden, also on other partitions)
These hidden system folders contain information for the Windows XP System Restore function. When you are finished with the setup of your Windows system and everything is working error free, I advise to turn off the system restore (Control Panel, System, tab System Restore). Enabling the option Turn off System Restore on all drives will empty all System Volume Information folders. It's difficult to remove the empty system folders from NTFS partitions (FAT32 partitions are no problem).
C:\PAGEFILE.SYS (Virtual memory)
The pagefile is only used when your main memory has been consumed by the running applications and more memory is needed. The use of the pagefile is temporary. Disabling the pagefile is only a wise thing to do if the available memory exceeds 512 MB (the use of the pagefile depends on the demand for memory of the running applications). You can also move the pagefile to another (faster) partition (as suggested on the page Windows XP settings part I) to make a quicker system backup/recovery possible.
C:\WINDOWS\Prefetch
This folder contains information about the regular started applications. Without any problem, you are allowed to delete the files in this folder (the files in the prefetch folder will be rebuild after a restart of Windows). The prefetch files in this folder are used for 'preloading' applications to start them quicker. At first you will probably notice a slower start of your favorite applications, but this will quickly be restored.
C:\Windows\$NtUninstall...... folders (hidden)
Those hidden "$" folders are waiting (and waiting.....) for a Windows update-uninstall. Of course, this will probably never happen! If Windows is working properly and stable after the latest Windows updates, you can delete those folders. The folder $hf_mig$ is the only exception to this rule. It is advised to keep this folder as it is, although removing it doesn't result in problems.
C:\I386\C:\Windows\Driver Cache\I386\C:\Windows\ServicePackFiles\I386\
Do you really want to save space? Delete above folders (or burn them on CD), but at your own risk! The I386 folder contains setup files (including hardware drivers). If everything is working properly, you won't need them, but if your system needs a change you might!
C:\Windows\Downloaded Installations\C:\Windows\SoftwareDistribution\Download\
These folders contain the setup files of downloaded and installed applications and Windows updates. The last one contains the downloaded Windows updates, which are there in strange names without any extension. With most of those files you can add MSI or EXE and run them separately. Saving these files makes it possible to patch them on another Windows system or Windows setup files.
Other temporary files (if still present, including the index.dat file):
C:\Documents and Settings\your username\Local Settings\TempC:\Documents and Settings\Default User\Local Settings\TempC:\Documents and Settings\LocalService\Local Settings\TempC:\WINDOWS\TEMP
C:\Documents and Settings\your username\Local Settings\Temporary Internet FilesC:\Documents and Settings\Default User\Local Settings\Temporary Internet FilesC:\Documents and Settings\LocalService\Local Settings\Temporary Internet Files
C:\Documents and Settings\your username\Local Settings\HistoryC:\Documents and Settings\Default User\Local Settings\HistoryC:\Documents and Settings\LocalService\Local Settings\History
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ERASING FILES WITH ACTIVE@ ERASER
I have very good experience with the Active@ Eraser for Windows application (download: www.active-eraser.com). With this utility you are able to delete your Internet & Local Activities. It will permanently delete files like temporary files, history files, recycle bin, cookies, auto complete lists and other personal settings. This is done by deleting the files and overwrite them with useless info (so you are not able to recover them anymore, even with data recovery software). With this application you are also able to erase already deleted files (read: the empty space) from your hard disk. The free version will overwrite the surface with zeros. (I prefer to use this tool before defragmenting and creating a system backup, it saves time and gives a smaller backup).
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DELETING LOCKED FILES
Sometimes it's not possible to delete or move a specific file or folder because the file or folder is locked by a specific process. To find out which process is locking it, you can try to find out and stop the process with Process Explorer (download: www.microsoft.com/technet/sysinternals/ProcessesAndThreads/ProcessExplorer.mspx). The process can also be stopped with the Windows Task Manager (combine the keys CTRL-ALT-DEL), tab Processes. With the tool Unlocker (download: http://ccollomb.free.fr/unlocker) it is possible to unlock files and folders by stopping the locking process. If it isn't possible to stop the locking process, then the MoveOnBoot utility can be handy (download: www.gibinsoft.net, see FileUtililties, old version is freeware). This utility makes it possible to move or delete files at the next boot.
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SEARCHING FOR POTENTIAL HARD DISK SPACE...
At this page many unnecessary folders/files are mentioned, which is a good start. If this still doesn't give you enough free space for you, it's time to do some further analysis to delete some extra files and/or folders (or if you are just curious...). The utility Disktective (download: www.freebyte.com/disktective) gives you this opportunity. Disktective shows by means of pie pieces the use of your hard disk. Another interesting utility is SpaceSniffer (download: www.uderzo.it/main_products/space_sniffer/), which shows rectangles.
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