I have a emachines C2480 that wouldnt turn on. So I replaced the PSU w/ the replacement model. Computer turns on fine now, all the drives are working. Now the Monitor doesnt detech the signal form the CPU. I connected my laptop to it and the monitor is working fine.

I have no clue what to do now?

When you replaced the PSU you checked all interior connections? I doubt there is an internal issue-- but double-checking is always good. This model-- does it have a separate video-card or onboard video? Sounds to me like a bad connection-- pull the cable off where it attaches to the back of the tower... check for bent pins -- try reconnecting. Then reboot.

welcome to the forum papanuch.

It could also be related to the video card itself.

Everything appears to be connected. All I did was remove the connectors from the old PSU and replace them one for one with the new PSU. Im only guessing that when the old PSU went bad, maybe it shorted out the video card? I have no idea.
Could something in the new PSU be wrong that is affecting the video card?

Is it a separate card--? Or Onboard video ? If it is a separate card... if you have another PCI slot... try swapping slots-- or at least remove the card, examine the small gold tips on the bottom / maybe clean 'em a little with a pencil eraser (gently)/ look into the slot itself make sure there's no "dust balls" in there. Then carefully reseat the card and reboot. There is a remote possibility of a connector problem with the PSU or (gasp) a motherboard issue. Try everything else first. Including swapping the video card. Was there an'event' that triggered the PSU dying ? -- power-surges/lightning, etc?

Becarful when installing a new PSU. Remember that if you are using a graphics card other than the on bored one mose of the newercards require to be connected to your power supply also which does not use the same connector as a molex (4pins) allthoguth it does come with a converter. Firstly check this is connected.

Secondly speeking from experence some mother boards need to have an axuillary power supply connector attached. This is the big long power conenctor and a 4 square pin connector. You probably already checked these but thoguth id mention it since ive spent over a day thinking "why?!" when i havnt pluged in that aux connector.