What is going on here?

Okay, I’m not a techy so I’ll try to explain my issues the best way I can. Recently, my husband got a new computer and now I am using the laptop that we use to share as my sole computer. We cleaned it up and reinstalled Windows Vista so that I would have a clean slate to start with. I installed the free home version of Avast right away, as I have used it before and liked it. My husband thought that it was creating problems with our laptop previously, and had removed it. He has McAfee now and I needed to have an antivirus on this laptop, so that is why I went with Avast. Every since the download, my connection is very sluggish, pages llock up on me, and in the last 2 days, my laptop with just totally shut it self down without any notice! This has happened about 5 times now. I have run the scans and there has been no viruses detected! What is the deal? I am going to unistall Avast and see if that helps. Can anyone give me any advice?

well first give us the result once you’ve uninstalled Avast… just to make sure that it comes from it (bad install or whatever)…

What did you actually reinstall? Was it a standalone Microsoft Vista package, or the vendor supplied package that contained demo copies of things like Norton or McAfee?