ever since i was updated 4/11 i keep getting false messages that i'm infected

ever since i was updated 4/11, i keep getting false messages that i’m infected when going to my known websites and unable to go there
so i went to system restore, chose the day before this occurred, and went to manual update on my avast free 5.1.889, virus definition version 110410-1, and have stopped updating, now i can go to my websites without interruption, but how can i stop this from occurring and continue to update without fear,

avast free version 5.1
windows xp home edition

https://blog.avast.com/

Check the post about the bad virus definitions. If you simply update to the latest ones, you’ll be fine.

If you accidentally put legit files into the virus chest, read the post about the bad definitions followup

followed your advice, seems fine now, let you know if problems develop, when can i dump the virus chest contents?
thanks alot

Rescan the chest contents inside the chest.
If they turn out to be clean: restore them.
If they turn out infected: keep for 2 or 3 weeks, rescan occasionally in that period in the chest. If still infected: delete after 3 weeks.

You need to update to avast! V6.0.1000

Plus you need to update your signature

Windows XP Home Edition version 2002 SP 2
Avast Free Home Edition Version 4.8

More importantly than the avast update, Internet Explorer should be updated to at least version 7, if not 8, and SP3 installed.

Sounds a lot like you have a cracked version of windows though.