Solid beep like that I would look at the following:
Memory, remove and reinstall, if it has multiple sticks, try one at a time (or two at a time it is built in pairs)
Clean the memory contacts, canned air or air compressor
Could also be the motherboard
being of XP vintage, some motherboards were made with bad capacitors, look at them, if they are leaking goo, or look exploded, they are shot. Motherboard would need to be replaced or the capacitors would need to be replaced, may not be worth it
could be the power supply, but rare
CMOS Battery, that is rare for it to send a solid beep like that, the CMOS battery holds the date and time and system setting like hard drive boot order, etc. The system should still turn on and display something even if this was dead/non functional
Good luck
Beep codes are mobo-specific.
1) look at the board and get the model #.
2) internet search for the model and “beep code”.
3) resolve issue.
4) Install Linux Mint