You could run a virtual machine. That means you could run a mini version of windows 98 on windows xp. AKA: run one OS on another.
If your not very good at computers i don't reccomend it. Otherwise i don't know.
Are these games on a CD or downloaded from somewhere?
You could try this - find the actual game file (probably a .exe file), right click and select Properties. Then go to the Compatibility tab and tick the box for Compatibility mode. From the drop-down box select Windows 98.