Before you begin the actual upgrade process to upgrade a CRM 4.0 instance to CRM 2011, make sure you have all of the resources required to complete the task.
Here are a few things that might stop or delay you:
Active Directory Access
Make sure you have the proper permissions to the Organizational Unit where the CRM security groups reside. You’ll need read/write access to the OU and all of its decedents.
This is easily overlooked, but make sure you have way, way more disk than you think you need. Between the various SQL backups you’ll make, and the extra temporary disk space the upgrade will take up, you could easily run out.