I have a case that is several years old so i bought a new ONE.
When I transfer the components and start it up i GET 1 long loud beep and nothing coming up on my computer monitor. (sometimes a get more than 1 long loud beep).

Obviously i thought perhaps the power supply is bad BUT all the fans are spinning, lights WORKING...
My computer even makes its normally loading sounds complete with windows start up noise etc at the appropriate time.

I have no idea what the problem could be. When i transfer my components back to my old case it works fine EXCEPT the odd time i get a bug while starting something like
Please re-setting CPU Frequency in the CMOS setup

HARDWARE ETC:
Operating System: Windows HE with the latest service packs
Motherboard: Nforce4 A939
Processor: CPU AMD 3200+
Video Card: Geforce 6600 GT
RAM: 2 gigs
CASE: old one is 230W, new one is 420W

Any ideas?Well after transfering my computer to my new case to the old one back and forwards 20+ times i have gotten it to work now.

For reference these are the THINGS i made sure i did this time / changes i made.

1) I made sure all the MOBO standoffs were in the correct holes including no screws in the gaps in my MOBO where there is no corresponding case screw.

2) I bent my video card metal strip thing so that i can get it better into the slot (which means i cant screw it in as it is now).
I dont know whether it is possible to have the video card partially in so that you get power/fan only?

3) I havent installed my case fan.

Sounds like something just wasn't in right. Depending on the motherboard manufacturer, the beeps could mean different things.

I advise you screw the card in though.