Hello and welcome to fixya.
In your case, im assuming you refer to the "Vista sticker" that is on the laptop. If a computer is vista-compatible this doesn't mean that it is not able to run older Operating Systems (such as Windows XP SP2) as well.
The sticker on the laptop just referes to the type of Operating System that came pre-installed with it. Now if you bought the laptop and asked your salesman for a DOWNGRADE TO XP
Operating System or if this is what he understood then it will probably come with Windows XP instead of Vista Home.
This also applies if you are working for a company in which case the company's IT Department will decide what type of Operating System is to be installed on this computer.
Overall: Newer computers/laptop models that support Windows Vista can also run Windows XP
ALSO: Check for the OEM sticker in the back of the laptop or bottom (it looks like THIS
for XP or THIS
for windows vista Home Premium). This determines whether you can use a vista DVD to upgrade your computer later from XP to Vista.
If you have any more questions just let me know.
Regards from FixYa.com