This is the information it collects and sends every 2 weeks
[WGA Notifications and Firewalls
Some personal firewalls, though not the basic one in Windows, may alert on the method by which wgatray.exe is started, in the case of Outpost firewall, it is identified as a "hidden process". The wgatray.exe process itself can be firewall blocked, without apparent problems. Removing the reference to WGALOGON.DLL using HijackThis appears to effectively de-install this update, to the point where it will be offered again if it has not been marked "do not show".
A tool has been released by a firewall vendor to prevent WGA Notifications transmitting information from one's PC.[8]
[edit] Data collected
When the WGA checks your system to see if it's genuine or not, it checks the following:[9] [10],
BIOS Checksum.
MAC address.
Hard drive serial number.
Language version of the operating system.
Operating system version.
PC BIOS information (make, version, date).
PC manufacturer.
User locale setting.
Validation and installation results.
Windows or Office product key.
Windows XP product ID.
[edit] Spyware accusations
The notification tool has been accused of spyware-like behavior, "phoning home" on a daily basis.[11][12] Microsoft subsequently admitted the behavior, but denied that it amounted to spyware.[13][14] Following pressure, Microsoft announced that in future the tool would only phone home once every two weeks, instead of every day.[15] Microsoft has also provided removal instructions for the pilot version of WGA.[7]
Despite this, Microsoft is currently being sued under anti-spyware statutes over WGA's non-disclosed "phone home" behavior.[16] The outcome of the lawsuit has not been determined.]