Leila:
I have heard that Windows XP Home is not so great in an office environment (Bert, feel free to chime in here).
I have a lot more demand on my system than you do and I get great performace, without a server. Well, I do have my database on a bigger faster computer and I don't run much else on it, but it wasn't expensive, and I don't have it set up as a "true" server, with a server operating system and all that.
This is what I bought, by the way:
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=2606265&CatId=3370Al is probably giving you good advice, though some of it is over my head.