Gearhead Garage

I bought this game, "Gearhead Garage" from Amazon.com. It said you could play it on Windows XP, but when I installed it, I can't even open it to play. There is a box and it has the word "GO" on it. When I click it, it freezes and then you have to press Alt, Ctrl, Delete to bring up the box to cancel. It says it isn't supported by a NT service and apparantely that is what I have. I can't get my money back and I want to play it. Do you have any suggestions? Also, I have an old computer here that also has Windows XP on it, it is for my kids. I wouldn't mind stripping XP from it and installing Windows 98 on it. Do you have any suggestions on how to downgrade the Windows in it cause It won't let me. Do you have a website where I can get 98 for free?