At BitDefenders online offer, I upgraded from BitDefender Antivirus 2010, to BitDefender Internet Security at the end of Jan2011. The Program worked for aprox. six weeks without problems, after that, I could not perform Full or Deep systems scans. I contacted BD on numerous occasions, was advised by them what to do, including removing previously purchased software that, according to them, clashed with their software. I followed their instructions, and still can't use the program.