Computer won't let mouse work...

[iSapphist!]

Yeah, I know the title makes me sound like a dumb@$$. ANYWAY, like the title says... my computer won't read the mouse, or something. When I get to the login screen, the cursor won't move. I'm sure it's not the actual mouse itself because I've tried a different one. I think it might be the connection, because the problem started when I was listening to music on the comp and my knee hit the tower (it's on the floor because there was no room on the desk) and the CD drive opened. I pushed the tower back a bit so that I wouldn't hit it, but suddenly the cursor wasn't working. I checked the back to see if the cord had fallen out, but it was still in. I noticed that it was a little bit loose, though. I've tried unplugging and plugging in again, with the computer on and off.
The mouse is optical, and I the computer is aWindows PC. It's a few years old. Apparently the brand is Compaq Presario, if that helps at all. The mouse's cord is a USB cable, but we plug it into a little green thing with a round plug on the other end of it, and put that into the mouse port in the tower. My momsays it might be because there was only 3% memory left on the hard drive, but I don't think so. I'm really sorry I don't have more information. I'm not the least bit techno-savvy, so I don't know all the technical jargen that you use...
Please, please, please help me! EVERYTHING is on that computer! My life! And we CANNOT afford a new computer OR a professional to come check it out. I'm desprate, seriously.

[computeruler]

try plugging the mouse into a usb port instead of the one its plugged into now

[iSapphist!]

I've tried that.

[drmsucks]

Borrow a different mouse and try it.

[iSapphist!]

I already did that.

[drmsucks]

Did you try a PS/2 (Round plug) or a USB mouse? Remember, BEFORE you connect or disconnect to/from the PS/2 socket on the computer, you must shut down the computer to avoid damage. If USB, you can connect/disconnect with the computer on.

If you tried a PS/2 mouse, try again: shutdown the computer, plug in the mouse, re-start the computer.

Post the exact model # of the Compaq Presario.

[t_blake07]

Did you try a PS/2 (Round plug) or a USB mouse? Remember, BEFORE you connect or disconnect to/from the PS/2 socket on the computer, you must shut down the computer to avoid damage. If USB, you can connect/disconnect with the computer on.

If you tried a PS/2 mouse, try again: shutdown the computer, plug in the mouse, re-start the computer.

Post the exact model # of the Compaq Presario.

Not sure about USB, but with the PS/2 plug, wouldn't the PC need re-booted in order to recognize the input device/mouse?

[drmsucks]

Did you try a PS/2 (Round plug) or a USB mouse? Remember, BEFORE you connect or disconnect to/from the PS/2 socket on the computer, you must shut down the computer to avoid damage. If USB, you can connect/disconnect with the computer on.

If you tried a PS/2 mouse, try again: shutdown the computer, plug in the mouse, re-start the computer.

Post the exact model # of the Compaq Presario.

Not sure about USB, but with the PS/2 plug, wouldn't the PC need re-booted in order to recognize the input device/mouse?

Properly done, the computer will be OFF when the PS/2 device is connected, then the computer will be powered on.

[t_blake07]

Right. I'm just trying to give the O.P. some knowledgeable reading.

You explained it well though.