Here is some guideline on how to perform upgrade from DPM 2007 to DPM 2010. Make sure your existing DPM is running DPM 2007 (64x) before proceed with below steps.
1. Install DPM 2007 SP1. You can get it from http://www.microsoft.com/downloads/details.aspx?FamilyId=8AE5EDAC-4DE8-44E0-A6F9-8AFBB3E23585&displaylang=en
2. Install hotfixes from http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=74ac7461-dbfe-4bc1-85a2-4d2948f30e42
3. Existing server has 3GB of free hard disk space.
4. Run DPM 2010 installation. It will perform the upgrade process.
5. Once the upgrade process complete, remember to restart the computer.
6. Then perform the following steps as recommended.
7. Before upgrade protection agents, make sure you have installed SP2 for windows Server 2003.
8. Use DPM 2010 console to upgrade the agents and perform consistency checks on all protection data.
Not too dificult and the process is quite straight forward. For precaution measure, please remember to backup the DPM database before perform the upgrade process.