XP Home CD?

[CalcProgrammer1]

Yeah, I did this for my Windows 2000 laptop (I figured, it's old, so what) because I bought it used, had a COA on the bottom but didn't come with any CD's. Can you legally transfer a copy of Windows from a PC to another? I installed Linux on my laptop, so I installed 2000 on my old desktop using my laptop's COA. I'm still only using one copy, but is it legal to move it from one PC to another?