“This app is slow”
See if this thread helps: http://forums.sandisk.com/t5/All-SanDisk-USB-Flash-Drives/trouble-with-secure-access/td-p/265981
“Because of this I want to uninstall it”
No need to “uninstall it”, simply delete the folders on the drive.
"I would like to install U3"
Unfortunately it can’t be done. 
