HP Pavilion VS Windows XP

My HP Pavilion(i think that's what it is) had Win98 installed and some form of WinXP as well when it came to be in my possession. The XP expired or something because it started telling me I needed to get some number from the company(Microsoft I think) to be able to use it.:confused It did this at the point of logging on to one of the users. I had no intentions of doing that so I wiped the HDD to install the OS myself, having the OS CD. When I tried to install XP to this computer, it told me(when I tried to run the setup.exe located on the CD) that I could not run this program in DOS.:cry So instead I installed Win98. If there's a way to install WinXP, I would love to do that instead of Win98. Any ideas as to why I'm unable to install XP on my comp? Enlighten me plz.

 

Nvm!