I was wondering if APPLE MAC OSX LEOPARD V10.5 can be installed on any PC, or is it only able to be installed on Apple computers?
Pretty much apple only. It is optimised for their hardware and doesn't have kernel driver modules for most other hardware. the drivers are not available. MAC OSX is closed source so if a piece of hardware doesn't work that's it.. nothing you can do. If you want to use similar (non proprietary) the closest is OpenBSD.. unix without paying stupid money to apple.
but remember you have to find the right image. i have tried several for osx86 some boot some wont run or freeze. I would recommend getting a mac mini they are cheaper and you can use any keyboard or mouse or monitor with them.