do you have another sysm you could test parts in?
try taking out the graphics card and powering on the system,
if it stays on and then beeps because the gpu is missing then you'll know that the rest is fine.
I dn't think that you need to take out the CMOS battery as you're not trying to reset any settings.
assuming that you've shorted your graphics card then the test outlined above should help.
it could also be that you've damaged the PSU, or main board, or even the processor... it could be practically anything. you'll just have to try testing each component individually.