The answer is mostly yes BUT,
what type and model of computer? That's the important consideration.
Many computers that were pre-loaded with 7 will not allow installation of XP. It's in the firmware.
Yes you can install win XP, you just need to make sure you have all the drivers for XP.
Where I work we have replace all of the win 7 for win XP on Lenovo desktops and laptops.
As long as your dont have a prebuilt machine you shouldnt have any problems- but as stated if you do- everything is hardcoded with firmware and such, and your stuck with 7. Why are you uninstalling 7 I think should be asked here.