Changed from XP to Win8, External PM Wants UN, PCONFIG "can't run on this PC"

So, my Windows XP computer died and I switched to a Windows 8 computer. Been running PM 4.6 on external drive. Now it asks me for a username before starting when I click winpm-32.exe. No clue what that un might be, it’s been years since I’ve needed it. Any un I try “doesn’t exist.” I thought I might change the drive letter with pconfig.exe (since the drive designation has changed with the new computer)--but when I click on THAT I get a msg saying ‘this app can't run on your PC.’

 

I see others are using PM with Win8, so don't know what the problem is. 

Help?

Thanks!!!