I think you have been misinformed again. Drivers can be downloaded free. You just need to know which to download and there are plenty people who with a bit of PC knowhow can keep you right or go into the Dell site and download the drivers for you particular PC and O/S. Salesmen have been known to be economical with the truth to get the sale. It is worth checking and establishing whether the drivers are available for XP AS A CONDITION OF SALE. Personally I would not buy a Dell PC for a DAW. They do not have enough specs that you need and come with lots of stuff pre installed you pay for but will not need or ever use. If you go down the PC route I would suggest a custom build. There are a number of companies who specialise in building such machines to proper DAW specs. I would suggest a water cooled noisless one for a start.

Here is a link to an article that might help with specs for a custom build.
http://www.futureproducers.com/forums/showthread.php?t=272047

Here is a link to a custom build site I googled this so cannot recommend them but it will give you some idea of what is available and costs etc.
http://www.digital-groove.com/gm/

http://www.soundclick.com/bands/songInfo.cfm?bandID=687727&songID=5238055