Roebuc 0 Junior Poster

Hey all, I have a XPS M1730. I have Intel Duo 2.4 GHZ and 2 GB of Ram. I noticed last month every once in awhile my hard drive would get overloaded and the computer would freeze for about 30 seconds. Last month I was running Vista, and most of the time when it froze it would go to a blue screen and I forget what the error was but I had to reboot. I decided I wanted to put XP Pro on it so I just went through that process. At first it has run great. No problems with my games or any programs, even Office 2007 runs faster but the last week I have noticed the hard drive working a lot again. It doesn't do it when I run games or any major programs. Most of the time it happens when I am using Firefox or Thunderbird. I will just get this hard freeze again for about 15 to 30 seconds. However now I do not get a blue screen, it comes out of it and everything works fine. Any ideas what could be the problem? Thanks.