I upgraded from Vista Business to 7 Pro last weekend and it was a smooth ride..I have a 320Gb HDD partitioned into 4 logical drives. The system partition is 236Gb.When I had Vista, it had a free space of 157Gb (Total used space 236-157 = 79Gb and this has been going up and down 3Gb with regular windows updates).Immediately after upgrading to Windows 7, it showed a free space of 160Gb, which fluctuated around 158-159 with various drivers install & uninstall activities I've been doing the past 3 days. (so space used with Win7 ~78Gb)Today I cleaned up the drive using Disk Cleanup and also removed all the restore points, just retaining the most recent one.The free space went up to 198Gb! So space used = 38Gb! I have all my documents, picutes, videos etc intact.Could someone throw a light as to how 50% space recovery could be made with just cleaning the restore points the first time. I understand upgrading to Win7 from vista will take a full backup of the drive and have it as a restore point; but with Vista and Win7 + Vista backup, the free space remaining was still the same.

Windows also uses space for Shadow Copies, essentially single-file-restore-points. Give it a try: find a file you've been working on off and on over the past few weeks, right-click and go to Properties. Then look at the Previous Versions tab. You'll see that you actually probably have 10, 20, even more copies of that file. Just in case you need it. Windows manages the space used by these backups automatically: if you need more space, it starts throwing out the oldest versions. If this was helpful, please vote by clicking the green triangle. If it solves the issue, click Propose as Answer. Thanks!

Hmm...could be the case of single file restore. But I usually keep my work and personal stuff in another partition which does not have the 'restore' enabled. Now that I've deleted all restore points, I don't see any prev. versions but I've noted it down and will monitor it for next few weeks. Could it be that all restore points are stored in C drive?I used Vista for about 5 months and I never saw the free space go down (if it was backup-as-you-go strategy) OR could it be that Windows earmarks the space for backup-restore and never releases it for normal activities? as I see the space reserved for system restore is 18% or 43Gb.

Man I wish I understood how shadow copies worked on a deeper level. I don't know if the OS even reports them in a drives' freespace totals. There's something in NTFS where data can be stored in some meta-space layer, technically in the file, but not shown in the file size? I can't remember exactly how to do it from a cmd prompt, but you can, for example, embed an MP3 into an empty txt file, and the filesize will report as zero, and the text file is still empty, but that MP3 is still there to be extracted. I've been lead to believe that shadow copies work off that NTFS 'feature'. If this was helpful, please vote by clicking the green triangle. If it solves the issue, click Propose as Answer. Thanks!

Wohoo..good insight! thanks for your responses.