It appears that system restore feautre of win xp does not works with Avast 4.8 Home similar to that of nasty Norton security software.
Recently I installed yahoo messenger before installing I created a system restore point and went ahead. After some time I decided to uninstall yahoo messenger after installing i used system restore to revert back my registry keys and leftover in program folder.
system restore was incomplete with a messege no system change occcured.
On checking the registry yahoo leftover were present same in program folder( althoug they are harm less )
point is system Restore feature does not work as expected