Upgraded my Dell Inspiron 15R by mounting the iso I created from install.wim on a Oracle VB VM using WHS's ESD Converter tool. I copied the install.wim to the ESD Converter folder on my Lenovo 450K 3.4 Quad Core with 16GB ram and ran it there to generate the iso. Took about 8 minutes.

Copied the iso to my Dell Inspiron 15R then right clicked on it and selected Mount.
Ran startup.exe from the mounted iso to upgrade from 10041 to 10049.
4 to 6 hours later (not sure how long as I went to bed) it finished and I have a fully functional laptop at the 10049 build level. Is there a log file of the upgrade and if so, where is it?

No flash drive or DVD needed, very nice and easy way to upgrade.

Surprisingly, no Windows.old was created. I had deleted Windows.old from the 10041 upgrade before doing this upgrade.