Well you can run XP on a mac with boot camp if you have a copy.
Other than that, I know you can order Dell's with XP (you pay more I think).
You have 2 choices, The standard entry level Inspiron, which handles pretty much anything a normal user can throw at it, including some gaming. The XPS models which are more expensive since they appeal to the gaming crowd and have a real video card.
The links I have added are for the 15.4 models, as they are almost universally the most economical for the power you are getting. These are base models, and with the exception of the 15.6" at the end might require some RAM upgrades.
For non gaming uses the Inspiron is the best bet, starting at $499:
http://www1.ca.dell.com/content/prod...ref=lthp&s=dhs
If you do game on it, or need some extra video power (doubtful for business apps) then the XPS at $1099:
http://www1.ca.dell.com/content/prod...ref=lthp&s=dhs
Edit:
I just noticed they have a new Inspiron model that is 15.6" that includes 4 gigs of RAM and 250 HDD for $559
http://configure.dell.com/dellstore/...&OC=NI152_F_2E
2nd Edit: The more I look at it, this last one looks like a fantastic value with those upgrades.