I dualboot win2k (server edition, but same kernel) and 98se on one partition, and have never had problems with it. Some people like to have the OS's run on separate partitions though.
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If i was to dualboot 2k and 98 how would i go about drivers??"
Download them off of the internet. Win2k will install many things without needing the drivers, but it's always best to get the latest drivers from the manufacturer.
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also would i need more RAM??"
How much do you have? Win2k professional will run well with 128, but 256 is better. I have 768 megs on my server, but never use more than 190-200 megs at a time (RAM is cheap

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and how much HD space does the 2k install take up?"
about 500 megs plus swap (like pulpp said).
pulpp hit everything right on. install win98se first, then win2k. You will have an option when you turn the computer on to select which OS (windows 2000 professional or ms windows (98)).
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yes but cont the drivers conflict if i have 2k and 98 running around? "
The drivers will not conflict. Windows 98 will install to the c:\windows directory, and windows 2k will install into the c:\winnt directory. As long as the drivers are installed correctly, win2k will not utilize win98's drivers to run your hardware.