If you don't want to wait on it, you should be able to "force" it by doing the following:
- Go here and download the Media Creation Tool: Link Removed
- Run it, and tell it you want to create installation media for another computer (second option)
- Create an ISO (not a flash drive—at least, not yet)
- Either burn the ISO to a DVD, or copy the contents of the ISO to a flash drive
- Run the disc or flash drive from within Windows 7 to perform the upgrade to Windows 10
This worked flawlessly on my laptop (also running Win7). My desktop's having issues...but then, my desktop has a really oddball configuration.