My guess is that it got its gold watch and retired...that is one elderly machine!!
Kidding aside, 'check' all the connections by dis-connecting and reconnecting, then check switches to make sure they are properly 'on' and then try to start.
No fans, no beeps, nada...then sounds like PSU has bugged out...and, yes, there is a fuse...but it is dangerous to open the PSU. If you are experienced with high voltage (really high - blow you across the room high), then you might try to replace fuse - but entirely at your own risk. Just as likely to be a bad cap (15 years old!)
Replacing PSU is safer, but I doubt it will be easy to find a compatible PSU (one built to work properly with this aged gem - Dell had some proprietary wiring back then so double check and make sure vendor stands behind what he provides).
Late thought, check the actual power switch on case, it may be broken.