I have a problem with my computer, but it's hardware related, and I'm not that good at that.

Sometimes when I try to start my computer, the screen just stay black and the computer make some beeping sounds. All I know is that it can happen when something is missing. I change nothing in the computer, and sometimes it just does it, and no matter how many times I retry, it still does it. I manage do fix it sometimes when I move my cables around a bit, and I'm suspecting my mouse, but I'd really like some help.

Anyone have any ideas?

In my experience, thats the video card being loose inside. Perhaps when you move the cables, you moved the video card inside abit.

Beeps on boot can mean several things, as follows;
power supply failing
keyboard connector loose
mouse connector loose
video card problems

Recommend you reseat all connectors(with POWER OFF) and try again. If the CP has been moved recently you may need to open it up and reseat the cards on the mobo.

If you have the motherboard manual, it should tell you which sequence of beeps mean what.

If you're comfortable with it, open up the case, and reseat everything inside, as well as outside.

If the screen is staying black it isn't just the mouse but something close to the vidcard or possibly the power supply. If you mean you get a black screen, then it boots on eventually it could be something more trivial. But your mouse is working fine during these times right? And the mouse not being detected wouldn't stop the system turning on.

My first system had symptoms like this and it turned out to be the old Banshee card wasn't connecting to the mobo properly. I'd open your CPU and tighten everything, check all cards etc.(not too tight btw) and make sure nothing is loose. Check for dust and do a standard cleaning.

I had this problem at work, you get beeping and no boot. I switched my memory from one slot to another, I have a bad mem slot. Try that it may be as easy as that.