Did you buy the laptop retail or online? If you opted to get some recovery CD's with it, you may want to use that to re-format the laptop, otherwise you may need to get into touch with Acer about ordering one, or possibly going for a copy of Win 7 and formatting it using that instead.
The first thing you need to get done is backing up your data before you take any action.
Aside from that, what anti-virus are you running? Are you sure you don't have a virus thats messing with you?
How old is your laptop? If its a Vista system with 1gb (inadequate by Vista/Win7 Standards) I'm gonna go ahead and assume its from the year 2006 or somewhere around there. If that's the case, your laptop may be on its way out. 2-3 years is all I'd expect out of a laptop. So maybe it might be time to explore some options concerning jumping ship to another laptop entirely.