Downgrading to XP is no trivial task, and can damage some laptop features, such as Media Direct, Symantec PC restore, ect..

 

Here is how to install software or drivers on Vista that are for XP
 
Right click on the setup.exe file for the software you are trying to install and select the compatibility Tab
Tick the "run this file in compatibility mode" box and then select XP in the drop down box, Tick "run as Administrator" if it is available, hit OK
Now double click this setup.exe file to execute the install process, hopefully all will go well and install the drivers you need.

 

After it installs, navigate to the program folder where it installed, then do the compatibility thing again for the program executable.

 

I do not guarantee all drivers or software to work but a large percentage do..
 
Good luck.

If the Software/  installer (exe file) is on CD, copy the entire contents of the CD to a folder in Vista, then do the compatibility thing.

 

 

If you do decide to downgrade, I suggest removing the Dell hard drive, replace it with a new one and install XP. That way if things don't work out, you can have Vista back, undamaged.

Extracting a tooth with no anesthesia is probably much less painful than downgrading to XP.

 

Good luck on this perilous road ....

 

(I'd rather buy a new XP machine...)