If you want to run OSX on a pc without it being virtual, you can do that too:
http://www.osx86project.org/
You can buy an Intel dual core PC (same cpu MAC uses) with a massive hard drive and 4gigs of ram for less than $1000.
A mac with those features would probably cost close to $2000 or more in some cases.
It's and interesting alternative if you are on a budget.
GIO, if you have a p4 2.66 you need standard ddr pc2700. That will be just fine in your dell, now you just have to decide how much you want, 512mb 1gb etc.