?u_.exe (Au_.exe, Bu_.exe, ...) and Second Life

While uninstalling Second Life viewer my Avast antivirus sandboxed uninst.exe. When I allowed it to continue running it spawned a process in C:\Users\<user>\AppData\Local\Temp\~nsu and the process was named Au_.exe. When I refused to allow this old well-known malware to run it spawned Bu_.exe then Cu_.exe etc etc. After I got to Ru_.exe I decided enough was enough and tried to end the process in the task manager. No luck. Ok, so I allowed it to run. SecondLife uninstall completed and I went in and deleted the temp folder. I don't know if it came WITH SecondLife viewer or somehow SecondLife viewer had become infected. I was removing a lot of other software and no other had that problem.