Having an unauthorized install of XP is not necessarily the end of your current setup, though if this recent reformat/install brought only a corrupted install then asking MS to assist may not be worth the efforts.
Here's a troubleshooting procedure for the unauthorized issue, posted by one of the MS helpers on these issues, Carey Frisch (Microsoft MVP)
1. Download and install the MGA Diagnostic Tool:
http://go.microsoft.com/fwlink/?linkid=56062
2. After running the WGA Diagnostic Tool, click
on the "Validation" tab and then click on "Copy to Clipboard".
3. Next, visit the following website and create a post in the
"WGA Validation Problems" forum and paste the
results of the WGA Diagnostic Data in a detailed post.
http://forums.microsoft.com/Genuine/...aspx?SiteID=25
4. A WGA troubleshooting specialist will analyze the data and
recommend an appropriate solution.
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