+ 1 Votes Found the problem!!! cyberghost_1 2 years ago After about 1 week working with MS Online Chat Tech Support... we were finally able to uninstall ALL Office 2010 programs... It was a mess!!!! BUT... when I tried to re-install Office 2010 I kept getting the same error about only one instance of Setup can run at one time... SO... I did some of my own troubleshooting and guess what... I found what was causing THE WHOLE ISSUE BEFORE AND AFTER!!!!! I'm using a Release Candidate (RC) of ESET Smart Securtiy... and it has a feature called HIPs... It monitors the changes made by any software on my pc... I disabled that feature... AND.... I was able to re-install ALL of Office 2010 programs!!!!