You need to re-activate reader. You can do this by going to this link and following instructions
http://www.microsoft.com/reader/info/activation.asp
Alternatively, and I prefer this method, you can backup the files that activate your version of Reader and reinstall those. Thay are called
- secrep.dat
secrep.dll
secrep.xml
secrepid.dat
Microsoft Activation.unload
and you will find them in the Windows folder of your PPC.
Obviously, thus time around you need to first re-activate your copy of MS Reader ;-)
[Edited to add the last file, Microsoft Activation.unload, because I overlooked it first time ...]