   Vista SP2 - freed up 10GB!
  I watch my system drive's free space pretty closely, since I only have an 80GB drive (Intel X25-M SSD).Vista SP2 said to make sure I had 3.3GB-5.5GB free before installing, so I made a note that I had 32GB free on my C drive before the installation.  Ten minutes later, it's all installed and rebooted, and I now check my free space again.  42GB free!Any idea what 10GB Vista may have deleted during the installation?  I had already freed up about 6GB by turning off Hibernation support a while back.  Anyone else see similar results?   
  Maybe it just hosed system restore data?   ;  On Windows Vista, when you install a hotfix or service pack, it doesn't actually overwrite files. All files that hotfixes/services packs install go into the Windows\WinSXS directory and the most recent version is hard-linked into your Windows\System32 (or whatever) directory. The reason for this is so that you can uninstall hotfixes and service packs in any order.When SP1 came out, Microsoft added a new utility, vsp1cln.exe, which removed old versions of DLLs from your Windows\WinSXS directory - essentially making your SP1 install "permanent" (because it deletes the old files, you couldn't uninstall SP1 because the previous versions no longer existed). Running vsp1cln.exe on my machine freed up about 5GB of space.My guess for SP2 is that Microsoft either ran vsp1cln.exe for you, or they've got a new one, vsp2cln.exe (or something) which the installer ran automatically to make SP2 permanent and also freeing up a bunch of space.So in short, all that extra free space probably came from your Windows\WinSXS directory.   ;  WinSxS is of course where System Restore mostly lives.   ;Quote:Original post by PromitWinSxS is of course where System Restore mostly lives.Yeah, you responded before I finished writing my post... It took me a while to find the name of that vsp1cln.exe tool :-)   ;Quote:Original post by PromitWinSxS is of course where System Restore mostly lives.I thought it lived in System Volume Information.   ;  An interesting note: All my newly-found free space is now gone with no explanation :-(  Too bad I didn't pay close attention to the sizes of individual important folders during this process, or it might have been instructional.   ;  have you reconfigured your system restore to use less space at maximum? maybe that helps?and have you run compcln.exe or how it's called?   