No need to keep the old computer around, donate it to somebody in need of one.

To play your games, if not working with Compatibility Mode (right clik on .EXE, then Properties, then Compatibility); modern computers may run virtual machines.

Use one of them, VMWare for example, and install WinXP (or Win98) in that virtual machine and play your games. If played in old PC, will play in new & virtualized.