hello mngong,
the edition of sql server and windows must match - 64bit sql on 64bit windows and 32 bit sql on 32bit windows.
On SQL2000 there was only a 64bit edition for itanium, so you must have such hardware.
SQL2005 have 3 plattforms - 32bit, IA64 for itanium and new x64. But still the plattforms must match.
Here you can find the requirements for SQL2000 IA64:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/sql64/in_preparing64_2ctv.asp
regards