Have Thinkpad with COE.Which xp version?

I recently purchased a Thinkpad T30 with a Windows XP Pro COA sticker. The previous owner wiped the hard drive, and did not have the original installation disks.

It is my understanding that I should be able to install a legal copy of windows.

Attempts to install xp using a couple different disks have all resulted in the error which reads: "Invalid Key..."

How can I determine the correct disks to use to result in a legal copy and installation?
Thanks in advance,
Bob

 

Obviously I could go out and purchase any version I want. But should I have to?

I thought that the COA sticker gave me the right to a copy of XP on my computer. I have been under the impression that the Key is linked to the sticker, and license to a legal copy, not to the individual CD. I'm not trying to move an OEM from one machine to another, nor am I trying to install it multiple times. I just want to reinstall the software to which I thought I had the right to.

I have also known (maybe wrong) that the keys are different depending if the key was originally from an OEM or Retail version.

I guess I'm confused as to why Windows installation tells me that the (authentic) key I've just entered is invalid?

 

In the weeks that have passed, I have skulked around and discovered:
A few oems use full retail installs.
Some BIG resalers (i.e.Dell and a few others - they have their name on the coa sticker) use an in-house customized oem install.
Other companies, in my case IBM (even though they too have the ibm letters on the coa sticker), use a standard full oem install.
None of the instances above can utilize another's install disc successfully.

I had two choices. If I needed to upgrade - that is absolutely had to upgrade and not loose data, my only option was to purchase a full retail version which would have installed over what was there (a bootleg commercial copy) using the coa on the new box. BUT I already had a valid coa and didn't care too much for putting out another 250 bucks.

My original question was how to utilize the original, valid and legal coa originally applied to the bottom of my Thinkpad. The one and only correct answer was to determine the type of oem originally used (turns out that ibm uses the full standard oem). I simply borrowed the correct disk, did a complete reformat (after backing up data) and install.
Input the coa serial number from my (computer's) bottom and voila!

Online validation failed (I had replaced the hard drive which was the start of all this)

A four minute phone call, pressing about 30 numbers into the phone keypad, then inputting another couple dozen on screen, and I am back where I wanted to be - in legal-land.

Only problem, oem's are not typically eligable for upgrades, but watching my grad student son struggle with vista, I'm not certain I want to go there anytime soon.

Anyway, this is the answer, thanks for all your input.

BTW, I just wanted to regain my legal footing. I'm a clergyman - not perfect, but would like to think that I try to do the right thing whenever possible.