If you're brave enough (or maybe suggest it to next-door's 9 year-old!), open the case and disconnect the hard drive's ribbon cable (wide, flat with 40 pin connector at each end), then see if the PC will initialise to the point where it complains there is no hard drive.

If it does, replace the drive and use your CDs to set it up again.

If it doesn't, scrap it!

Sometimes a dead IDE drive (hard drive, CD or Zip drive) can drag the IDE ports down so the machine won't initialise and just sits there as you described...