Each make of motherboard has it own "beep" configuration to tell you what is wrong. Since it is beeping, it is almost certainly a component failure and not the HDD.
Most likely culprits are RAM or a fan failure. They are not the only possibilities, though. Either of those are probably easy to fix. Anything else would most likely be terminal because you'd probably need a new system board.
If you can find someone who can do a free fault diagnosis, in might be worth investigating but it is not worth throwing a lot of money at the device. Even a lowly but modern I3 processor machine would out perform your old PC by a margin.
If you suspect it's the hard drive, you might want to try swapping it out and seeing if that fixes the issue. As for the constant beep, that could be a number of things - could be the motherboard, RAM, or even the power supply. Btw, what do you think about Windows 11? Is it worth it? Btw, my father has recently got one of the windows 10 keys to (finally) upgrade his Windows XP. Yeah, such people still exist, lol. Anyway, keep us updated on your issue.
it was old like me but unlike me it stopped working pc destroyed now kept the good bits ie memory and HDD , and thats it, May get another later . Just have the two now another full size base unit windows 10 and a decent lap top with 10 too. After trying to buy a reconditioned one last week from Amazon and refused credit . "so called digital signature " i call it intrusion myself . Next one i will pay cash The last one died after 6 years or so ( was Windows 7 bought for £70 s/h with 10 on it) So pretty good value i thought so . This one is only 9 years old ex commercial company owned . Had that just after COVID 19 in 2021 .