What errors did you get?
Here are some possible reasons, quoted from other sources.
Microsoft SQL Server 2000 64-bit is for Itanium CPU's only. It does not work on an x64 cpu - the architecture is different.
There are three flavors for SQL 2000; 32 bit version, an Itanium 64-bit version and an x64 bit version. Be sure to have the correct flavor of 64 bit.