We have one Windows 2000 Server in our company with 10 CALS, we are using RAID and regular backup so our system is quite secure however that doesn't protect us from CPU or mainboard failure. If I was to setup another server to run ONLY when this main server was down for hardware repair (1 - 2 days a year max.) would I need to purchase another Windows 2000 Server O.S. with 10 CAL's or would it be ok to simply use the current licenses as this server will never be running at the same time, only when then main one is down. Any help appreciated.

Yes, that would violate the EULA, but there is a way around it, Buy the exact hardware that your current pc has, back up the entire hard drive using powerquest or norton ghost, and keep that somewhere safe, you are only allowed to have windows installed once on one computer at a time per license. if you have an image backed up for fault tolerance, that's ok, if you have a system built and ready to go, not ok.

I was afraid that would be the case, well, thanks for clearing that up, unfortunately its not possible to buy the same hardware anymore due to the rapid pace at which old hardware is being replaced by new.

I found my win2k license restrictions to be too restricting. It's all about them making every red cent they can get and screw your convenience. I switched over to Redhat, which doesn't require licensing, and I was able to do exactly what you're saying you want to do. So now if my server goes down, I have a backup, AND I can keep the backup powered up all the time (and updated) without having to shell out money to some marketing weasel for the convenience of it all. It took me about a week to get everything set up because I had to figure out the new OS from scratch, but it was well worth the time. I ended up with a more stable OS too. It works as a domain controller /file/print/backup server for Win2k Pro workstations. You might consider it.