I tried to install the outlook client for CRM 4.0 today, firstly i tried to upgrade from the CRM 3.0 Outlook client which it seemed to go ahead with (it gave the option to upgrade), but then failed when checked for the SQL instance for CRM.
Strangely enough, the new client had removed the SQL instance and was now trying to find it again......Bug?
2nd try, I removed all traces of SQL and Microsoft CRM by following Microsoft's KB article on manually removing CRM 3.0 Outlook client. I then ran the install, it installed the requirements plus the SQL instance and copied the files. Right near the end it started rolling back the actions and said the installation had failed. Another bug?
I followed this KB for removal: http://www.microsoft.com/dynamics/crm/using/deploy/removeclient.mspx
Any ideas? I shall try on some other PC's and update you.