I'm giving avast! (free) a bit of a run on my underpowered Belnea O.book (Vista with 1Gb RAM!), replacing MSE. I've removed the feature creep I don't need, something avast! allows you to do. I can open files of executables without waiting five minutes now. The updates are quick and I don't live in dread of the MSE update slowing everything to a crawl. avast! could be a keeper (on this laptop at least).