Client Install

I recently upgraded my PC to 64bit Windows 7 and have been attempting to install Notes 8.51, having previously successfully installed it on my old system, 32bit XP. Now, when I hit the Standard.exe I get a message back “Failed to launch process as specified user:740”. I get this when I attempt to run it across the network, when I have it copied to my hard drive and when I attempt a smart upgrade. Can someone advise how I get round this please. I have network admin privileges.Thanks

BB