video card change only with OS reinstal?

Hi there
I am planning to change my current video card (Gigabyte x1600xt) with an XFX 8800 gts 320 MB in a few days, but I'd rather not perform a clean XP instal before doing so...I have received advice that the best way to be sure that a new video card would work properly is an OS reinstal, especially if its about a complete GPU change, form ATI to nVidia. I have used DriverCleaner pro in the past but only to replace standard with optimised drivers for my x1600xt.
Can I dispose of the old ATI drivers with DCpro, then mount the XFX 8800 and instal its drivers or do I really have to do a reinstal, too :?:

Should it help in any way, the rest of my system comprises an E6400 on a GA-P965-DS3, 2 GB DDR2 GEIL ultra 800 mhz CL4, Seagate Barracuda 250 gb SATA2 7200.10 (OS) + Seagate Barracuda 160 gb SATA2 7200.9