Some programs that Microsoft created for Vista run just fine on Windows XP.
Windows Defender, the antispyware product, works on XP. Vista's initial version
of Windows Media Player, WMP 11, runs rings around its earlier incarnation,
as does Internet Explorer 7 ? but you can run both on Windows XP. Don't
pay for Vista if you have an XP system and you only want the latest versions
of Defender, WMP, or IE. You have better ways to throw away your greenbacks.
More than that, if the computer you have only supports Vista Home Basic (Probably because of an older video card), don't bother with Vista; stick
with Windows XP. You won't see much benefit ? literally and figuratively. On the other hand, if you want to take advantage of the many, manifest, and
truly compelling goodies in Vista, you could consider upgrading in the following
cases:
1.If you own a fairly modern PC (say, an Intel Pentium 4 running at 1.8 GHz
2.or so, or an AMD Opteron 144 or higher), with several hundred megabytes
3.of free disk space.
4.If you have 1GB of memory or you're willing to shell out the grub to get it.
5.If your video card can handle the load. Many laptops simply can't run Vista, and video upgrades rate as too expensive ? or just plain impossible.

I don't recommend that you try to upgrade to Vista unless you have enough
video power to drive the Aero Glass interface. For most Windows XP users,
that's the crucial upgrade decision point: