If you’re having trouble installing MySQL 5.1 on a Windows server, I’d recommend the following process. Don’t skip the first steps that describe the uninstall and removal of the previous install as this seems to clear up most issues. For the uninstall, I’d recommend manually deleting data files. Caution: deleting the data files will delete any data previously entered into MySQL.
1. Remove previous MySQL installs (and remnants)
a. Stop the MySQL service ( Start | Control Panel | Administrative Tools | Services)
b. Remove MySQL using Windows Add or Remove Programs (Start | Control Panel | Add or Remove Programs)