Here is a link to the service manual for the PC.
Scroll to p.80 to view the beep fault codes. Determine the pattern of the beeps (as shown in the manual) to find out what is wrong with the computer.
If it is 'memory' related, disconnect the power from the PC and then reseat the RAM modules, i.e. remove and replace and see if it works. If still not if there is more than one RAM module remove all except one and try again. If still no good try RAM in other slots. if still no good try the other RAM modules, one at a time in all the slots until it works. You might have a faulty RAM module or a faulty RAM (DIMM) slot.
Always remove / replace RAM modules (or anything else for that matter) with the power disconnected from the PC - not just switched off
If related to CMOS battery, look for a button cell battery on the motherboard and with a DMM - (Digital Multimeter- Voltmeter function) check its value. If you don't have a DMM replace the battery. These are non rechargeable batteries and usually have a life span of about 5-7 years.
Hopefully it is one of these and not a systemboard problem.