Hi w2k4eva, thanks for your answer. I want to read and write the drive from XP and 7. I don't use system restore on XP, I use it on 7. I disabled system restore and VSS service on XP but it is the XP driver volsnap.sys that removes restore points and previous versions from Vista and later, and it cannot be disabled.
So the only "solution" is never use a drive with Vista or later shadow copies on Windows XP.
I think the only trivial fix they could have done was to modify volsnap.sys to recognyze Vista shadow copies an NEVER, EVER touch them. Cause is inadmissible that an O.S. removes anything from an external drive.
I wonder how many times back in 2006, somebody plugged a Vista user USB drive into Windows XP and removed all previous versions in the drive. Or somebody took a Vista system drive with a virus and plugged into an XP machine to remove it, and every restore point vanished...