A bunch of tech questions

You can't just use your Windows partition for that? Unless I'm an anomaly, Ubuntu should be able to mount it just fine. (my Windows partition is NTFS)

Also try http://www.ext2fsd.com/ which allows you to mount ext2/ext3 (Linux) partitions in Windows. That means you can essentially access your whole drive from either OS. Convenient.

Of course, keep in mind that Windows apps still only run in Windows and Linux apps only run in Linux. (barring such things as WINE and emulators which don't help for already installed programs anyway)

 Spoiler

So I'm guessing that on a computer with a lot more memory you'd give ~20GiB to Ubuntu and the rest to Windows at this step? I don't think I would be installing more than 20GiB of Linux programs, and I've heard that it's not too hard to resize partitions once you've got them.

PS: I know this is kinda unrelated, but how is WINE "not an emulator"? It seems like it takes programs and attempts to run them like the original OS would run them, which is kind of the definition of an emulator.