I was online one night, and suddenly my PC froze. When I restarted it, it would not boot. There are no beeps. Both CD drive and CDRW flash, fan is working... but does not display, not even a blue screen.

Any ideas? Bad CPU, Motherboard?

Please advise, thank you.
J.

Almost definitely a hardware problem. You need to test RAM, power supply,hard drive, CPU, possibly graphics card, and motherboard. Swap with good ones if possible.
Also, if you can get hold of it, try to run Knoppix Linux. It's an OS that runs directly from your CD drive and can test your PC if the hard drive or Windows is broken. Won't help if the BIOS deosn't load ,though.
http://www.knoppix.net/

If it has an award bios try,booting while holding the delete key.If it doesn't start,continue holding delete and pressing reset.Try that a few times.If that doesn't work unplug from wall for a few minutes and try the above again.

If that still does not work you should try resetting the cmos jumper.It should be three pins with a jumper on two of them(check the manual for it's location).unplug from the wall socket and remove the side,ground yourself by touching a metal part of the frame and remove the jumper from the two pins it is on and place on the other and middle pin for a few seconds.remove and replace as it was.It should now start with default bios settings.

If the cmos reset doesn't help, try disconnecting ALL nonessential hardware, including the hard drive and any unneeded sticks of RAM.

Then try a boot floppy or CD-ROM (see knoppix link above, it's very good :) ).