diagnostics0 Pull out any extras - printers, game controllers, that kind of stuff.
Maybe pull some RAM out it might be a faulty stick.
If your pc is old then maybe the bios battery has gone flat or short circuit.
Faulty hard drive can slow down everything. Try pulling it out and booting from CD/USB.
Remove the CD/DVD drive as a fault here can also slow things down.
Take out all reasonable hardware - hard drive, disc drive, RAM, printer, UBs etc. Listen for and make a note of any beep codes.
