@Bercilak, I hope this still helps you, or at least this may help other users.
In Vista, "System Restore" and "Shadow Copy" are related, and the default is to use up to 15% of the Disk Volume.
AN IMPORTANT NOTE: Even when you allow Windows Explorer to show Hidden Files and System files, you will see that the folder named as "System Volume Information" is empty, no matter how many files are there. Using Windows Explorer, the "System Volume Information" will be shown as empty, always. So this does NOT mean "there *must* be data loss". There are several ways to know how much allocated space this special folder has, but Windows Explorer is not one.
There are several reasons for Windows to delete previous Restore Points. System Restore is not always active by default, and it depends on several parameters, including total Volume space, free space, if System Restore is active for that specific Volume (search Vista's Help for more info).
So, assuming all those conditions are matched, every time you install/uninstall some program, update windows, change drivers, or even defrag the Volume, the space Vista allocates to System Restore and Shadow Copy also changes.
Moreover, CCleaner doesn't really clean the corresponding files when you use its System Restore tool. Instead, it deletes the references to those files. This means that it is possible for Windows to think the allocated space for System Restore is almost full (though the user can't really make use of those files since the *references* were deleted). If this is the case, for every simple change you make to the Volume, Vista will delete previous Restore Points, but not immediately. The deletion of previous Restore Points will be executed while creating new ones.
So, when you say you installed new AntiVirus and AntiSpyware software, or when you delete System Files (including Logs), Vista tries to make a new Restore Point, and since there may be not enough free allocated space for that purpose, the previous Restore Points are deleted. And even if you don't make any changes of those that trigger a new Restore Point, System Restore may be making a new point if the programmed automatic frequency is reached.
Using multiboot systems also deletes all Restore Points. And if the Volume is FAT32, System Restore and Shadow Copy do not apply.
Most probably, your issue is related to the max allocated space to Restore Points being reached.
My suggestion is this:
1-Reboot your pc. This will free memory and/or files.
2-Close any non-essential program.
3-Run Windows Vista Disk Cleanup *as administrator*.
4-While in Disk Cleanup, choose to clean "for all users" (as opose to clean only your user profile).
5-Let Disk Cleanup scan whatever it needs to.
6-Select the options you want to clean.
7-Click over the "more options" tab, and select to clean previous Restore Points.
8-Let Windows Vista Disk Cleanup do the job.
9-When all the cleaning is done, wait for the HDD led to (almost) stop blinking, then reboot.
10-Make a new Restore Point.
Probably you will see now much more free space in your Volume than before, since Vista deleted files that CCleaner couldn't. There are more advanced procedures, but for now I think it's ok.
From now on, I would suggest to use ccleaner to clean temp files or application files, and leave system files alone, including Restore Points and Windows Log Files.
I hope this helps.