Using ConfigX or an editor, you can edit your xconfig file as per
http://www.redhat.com/docs/manuals/l...de/doc125.html and set your DPMSstandbyDelay to a hideously large number. You may also need to alter the offDelay and suspendDelay as well.
This won't completely disable standby mode, but if it is set to 100 hours, you can usually bet that there would be some user interaction in that time.