Windows XP/SP2 OEM- I don't quite understand what I've read. Help please?

I had to wipe my hard drive last year and reinstall Windows. Since I couldn't find my Windows XP disc, my son gave me his as he wasn't ever going to use it again. Everything went fine installing, but I couldn't activate it. I finally managed to get around that with a key he gave me and got around the 30 day-activation with something the reset the oobe.bnk. (Which I found on Microsoft's site.) That fix was only good for 4 uses. I was hoping to find a way to fix the activation issue but never got around to it.
Well, now Windows needs to be activated. One thing I didn't know until a few days ago is that the CD he gave me is OEM. I've read the stickies about changing VLK to OEM.
Is that something that can be done in reverse- changing OEM to VLK? I did use the oembios tool to make sure that my computer does have at least some of the things I read about. I just don't know where to go from here. Can it be done? There's so many different stickies and tools that I'm not sure what I could or should use here. Or am I better off just wiping the drive and installing another Windows version?

Oh, something else I wondered about- I can get on the internet and use most of my programs as long as I access c: through IE, which I get to come up by clicking the link in the activation screen. Is that normal? I keep thinking I'm not supposed to be able to do this.

 

vinodh- It's a Compaq that I bought used. I do know that it wasn't built by anyone, it had all the original factory parts when I got it. The only thing that has ever been changed was the power supply, which I had to replace. Thanks for the answer- that looks easy enough for me to do.

sebus- Only time will tell. I got this one working again last year when I was told I may as well look for another one. This time it works, at least.

 

Sorry about the double post, but I ran into a slight problem:

I created the XP Pro SP3 cd like it says to in the sticky. When it gets to the stage of entering the key, it's already there like it's supposed to be. However, it doesn't work. It says the key is invalid. I can't skip entering a key either- clicking "no" does nothing. It's a clean install as the drive was formatted first. Any help?