You should not attempt to update to Salesforce for Outlook 2.2.1, per Salesforce support, it is missing the Microsoft prequisite files and will hose the system you are updating.  The only way to fix is to do a clean install and then run 2.1.2 or 2.2.3.  Note:  The 2.2.3 installer was created for Office 2013, XP was not included and Salesforce is not going to do another update untill the Winter 2013 release.  I know several companies that are still recovering from the 2.2.1 update.