Dan, I might be able to help as I dual-boot now & have dual & triple booted various OSs for a long time.
1st confirm for me that I have this straight... you have 2 physically separate & distinct HDDs, right? 1, henceforth, I'll call Data drive and the other has 7 & a 50G partition for 8. If I have that all correct, here's my recommendation:
In the Win7 machine/OS, in Disc Mg't find the 50 G drive/partition. Format it.
Physically unplug the Data drive. You can reconnect after the Win8 install is done OR after it fails, again...just kidding.
Now, take your Win8 DVD & install to that 50G drive/partition. When done it will use the Win8 boot mgr and in msconfig you will see both boot paths & can make 8 or 7 the default in terms of boot order.
Please, let me know if I understood you correctly & if my suggestions have worked for you. Thanks.
BTW, I would consider 50G as minimum for size; once you start loading in programs & other software, well, it's none too big, you understand.
Cheers,
Drew
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