6 Beeps

Hi, fairly new to all this but I really need some help.

I have a studio xps and a while back I had a slight problem which resulted in a technician coming over to help fix it. It turned out to be nothing more than accidently putting my computer in hibernation mode! But he did change the graphics card, which I don't know if affected anything. But I'm telling you this incase it may have.

Now, about a week later I was playing a computer game when it began to freeze up until a point where it had frozen. The only way I could turn it off was from the power button, which I did. But when I tried to turn it back on I got the 6 beeps and it wouldn't start. Tried this over and over again and got nothing but the 6 beeps. So I called dell and what not, and ended up haveing to unplug any cables at the back (obviously turning everything off) and holding the power button for 20 seconds. I did that, and once I tried it again, it worked! Had to download a few stuff off dell, and from that I thought the problem was fixed! But then when I started playing any games, it began to freeze again. So when I had to turn it off and on, the 6 beeps were back! From this point the only time I got them was when I was playing a game and it froze, which resulted in the 6 beeps. So I had to keep doing that 20 second power button thing. I figured if it only happens while playing games (for some reason) then I'll stop playing them...but that can't be right!?

Then yesterday, without playing a game on it, when I turned it on I got the 6 beeps. So the only way to get it to work was through holding the power button. Now obviously this can't be right, and I'm actually typing this now on my computer because I got it to work, but I know when I turn it off and go to turn it on again, I'll get the 6 beeps. Can anyone please help me? :( I haven't changed anything in the desktop, and I do seem to be getting it work, and like now it's fine. So what's the problem? Thanks.

Perry

I have a Nvidia GeForce GTX 460 graphics card and running windows home 7 (if this helps)