Four beeps often indicate RAM problems. Remove and reseat all sticks. If you have four sticks, just insert two and try again; if no luck, try the other two. If you only have two sticks, just try one at a time. If you have defective RAM, you will need to find the bad one(s) by a process of elimination.
Verify that all cables (including power) are inserted properly and that all cards are seated correctly.
Do you have access to a different monitor, if only for a quick test?