Strange pop-up message

The first message that pops up when I open my outlook is.

Error in registery for extension "Exchange Extentions;?" The syntax or
format of the registery entry is incorrect. Check the registery settings and
compare the registery for this extention to the other extentions in the
registery.



Hi everyone

I have exch2003 and xp pro.the above message keeps popping up if one of the
network users go into outlook.He then has to click OK about 5 times and then
it dissappears and then he can continue working. Anyone got this before and
can help me




.