Try this:
Search your \Windows folder for "mshtml.dll" (making sure you search hidden files and folders as well as system folders and, consequently, subfolders).
Look for the hotfixes and updates involving mshtml.dll (they have "KB???" in their path).
Uninstall the corresponding fixes using "Add and Remove Programs".
Run "regsvr32 mshtml.dll" via "Start | Run...".
See if System Restore has returned.
Re-apply the fixes and updates.
(You can also try re-registering an archived mshtml.dll directly using regsvr32 to see if it helps, by running "regsvr32 C:\WINDOWS\ServicePackFiles\i386\mshtml.dll", for example. You can drag and drop the file to the "Run..." prompt.)
hope that helps,
-heinz
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Heinz Tschabitscher
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