MojoPac

https://portableapps.com/search/node/mojopac

It's been covered numerous times:

Windows XP Only - Won't work on 95, 98, Me, 2000, 2003, Vista or Wine
Admin Account Required - You have to be logged into Windows with an admin-level account. So it won't work at universities, schools, corporate offices, libraries, net cafes, hotel business centers, etc
Removable Drives Only - You can't install it to a local drive, network share, etc
Slow - Really only performs acceptably from a portable hard drive... not a flash drive. So slow their End User License Agreement forbids you from benchmarking it.
Legally questionable - Some commercial software specifically prohibits you from installing into a virtual machine. There's a whole section in their EULA to absolve them of responsibility for you doing this.
Registration required - You have to register with a valid email address to even try it out and your login and email address are tied to your install.
"Anonymous Usage Statistics" - According to their EULA, they'll probably be watching what apps you run in the near future

All in all, it has way too many shortcomings. So many that they recently gave up trying to charge end-users the $50 license fee and made it free for non-commercial use.