If you can, do the clean install instead of upgrade. If clean installation is not available, then you may have to do the clean install of Vista with the following upgrade of 7. If you are upgrading :
1. Save your data to a safe place
2. Format the partition
3. Clean install Vista on the formatted partition
4. Do NOT install drivers
5. If not integrated in your Vista installation, install Vista SP 1 & SP 2
6. Upgrade to 7
7. Install 7 drivers