Where do I begin?

Well I was able to spend about an hour on my wife's friends PC today. First off I'm not sure as I've had a PC that has been so slow. It's not the hardwares fault either . It's got 2.8 Ghz Pentium 4,80Gb HD, 256mb RAM. Every function takes its sweet time after you click on it. It's also got an expired antivirus. Also a pop up telling me I've got a Windows Security Alert with misspellings (obvious give away it's spyware). I'm still fighting to get it running. Did I mention it was slow? I'm sure I can get back in shape but it may take awhile.