Try reactivating office by following the below mentioned steps:
If you are using Windows XP:
1. Click Start ->Computer or My computer->C-DRIVE(c :) \documents and setting s\All Users \Application Data\Microsoft\ Office \ Data.
2. Right click on Opa11.dat->rename it to opa11.old.
3. Open outlook and activate it.
Check the link below for activation
http://office.microsoft.com/en-us/help/HA012334341033.aspx
If you are using Windows Vista or Windows 7:
1. Click Start-> computer-> C-Drive(c :)-> program data->Microsoft->Office->data.
2. Right click on opa11.dat ->rename ->opa11.old.
3. Open outlook and activate it.
Hope this helps.
Ruchi Bisht