AS7 has no special requirements beyond Java 6.
According to oracle's certificated system configurations java 6 should run just fine on Windows 2000 SP3/SP4.
Java 7 on the other hand requires windows server 2008 and newer systems.
In any case it would be wise to upgrade given that system is more then decade old and does not recive security updates anymore.
1 of 1 people found this helpful
And in regard to hardware, I would say that what was enough for 4.x will most likely be enough for 7.x
And even if it wouldn't be enough. Hardware and virtual servers are cheap nowadays ;-)