|Impossible to diagnose accurately without knowing the BIOS maker and the length and pattern of the beeps, but classic causes are failed RAM or faulty graphics adapter, so there's two things you can investigate.|
You can test the RAM with memtest86: http://www.memtest.org/
The only way to check for failed graphics adapter is to swap it out with one that you know isn't faulty (there is no need to install the manufacturer's driver just for testing purposes).
If the problem persists & you need to post for further help, please say what you've tried so far to to fix it. Giving you the same advice twice & just going round in circles will then be avoided.