Easy...
This is listed in Grisoft's Technical Support FAQ. ;-)

START/RUN
regsvr32 /u avgoff2k.dll
Click OK

To restart Office XP to request virus scans on opening documents..

START/RUN
regsvr32 avgoff2k.dll
Click OK

If you have problems with this do it from a command window in the directory where AVG was 
installed... usually c:\program files\grisoft\AVG7.

I've been using AVG for years now and I wouldn't change it. By far still the fastest free AV out there.