Sounds wonderful!
First off the system is too old to even be contemplating running Vista on it. Microsoft provided a tool for seeing if your system is "Vista ready" with higher and newer specifications as the guideline just for the Basic edition not Business, Home Premium, Ultimate, Enterprise in other words NADA! NO WAY!
Windows Vista Hardware Compatibility List
http://winqual.microsoft.com/HCL/Def...g_id=10048WHb1
With the newer case you are now running you first have to get familiar with actually running games in any version let alone Vista. Keeping things like video and sound drivers updated, general maintainence, adware/spyware/virus sweeps to see if anything got on. etc. in that sense.
At one time MS came out with a new Windows every 2-3yrs. while XP got a longer wind and too comfortable with the MS delays of Vista. Otherwise that would most likely have seen daylight in the 2003-4 time frame. XP would otherwise be totally outdated like 9x-ME, NT, 2000 already are while many still run some of the older versions. Some basic information on the newer pc could help a little while the MS page there gets you started with a tour depending your current system to see if it meets the basics.