Hi MIKEMAC
I'm not currently a Windows 7 "guinea pig" so I too am making assumptions.
Firstly, a 6.2GB 'pagefile.sys2' isn't "
a windows file that I downloaded straight from microsoft". (
How big was the entire download? )
Assuming that it is the legitimate paging or swap file for W7, it's created/recreated each time you start W7.
The reason it's is not detected as a trojan when you scan in W7 is that the paging file is deliberately excluded from any scan because it must only be accessed by the OS (If you try to scan it manually you'll be blocked by the OS.)
So even if the "trojan" detection in Vista is false, if you allow avast! to delete the file from Vista, W7 will just create a new one when you boot into W7.