Hello, today I was trying to install a new graphics card onto my grandmother's computer, as she has company all the time. At first, everything was fine. Her computer was running normally, except for the fact that it couldn't play games. So I tried installing the AMD Catalyst sweet, as the card was a AMD card. Well, after installation, I checked the install directory, and it was empty, so I restarted the computer. Of course, this didn't fix the problem. So, I read online and figured it was because of the onboard graphics the pc has, so I shut down the computer, booted and BIOS, but instead of changing the video card option to PEG (PCI-e), I accidentally hit normal PCI. After doing so, I restarted my computer and I got the dreaded black screen accompanied by 3 beeps; 1 long, 2 short. I am still unable to boot my pc without it, so could someone please help? Thanks.
* The card is a AMD Radeon HD 7450. If you need any other information, please say so below.
EDIT: I know what the beeps mean, just need to know how to fix it.