What's a good, affordable laptop (PC)?

I'm shopping for a new laptop to get me through a 4-year Ph.D. program. I don't want to spend an arm and a leg, but I do want a durable, reliable system that operates relatively quickly, has a decent hard drive space, has a good bit of memory, and is compatible with various programs, such as SAS. I would consider a Mac but the compatibility issue has made me wary. Now, I'm considering a Dell Inspiron with 4 GB of memory and a 320 GB hard drive. Does anyone have experience with this type of computer? If so, do you like it? Are there any other PC's I should consider? Thanks for your advice! :)