My instructions here - Manager will not launch - #13 by dalacor might be helpful for you in removing and re-installing Manager. Manager will not launch - #13 by dalacor
Basically you need to uninstall Manager from add/remove, completely remove any ngsoftware entries from registry, remove any Manager folders, reboot and then install again. Obviously backup your businesses first!
You are probably running a 32 bit and 64 bit version on your pc. Or trying to.
You need to check if you are running 32 bit or 64 bit windows 7. Windows 7 can be either. So you need to check that first. You are probably running 64 bit as its rare to run 32 bit nowadays.