EDIT2: This issue seems to have been fixed in 11.04, when installing it now has an option called 'install Ubuntu alongside X' where X is your other operating system. This was very helpful for newbies like me who don't want to play with hard drive partitions.
I would like to install Ubuntu on my laptop as my primary operating system while keeping Windows. When I get to the screen that says "Allocate Disk Space," I click specify partitions manually because I don't want to erase Windows.
Problem is, I don't know how to specify partitions manually. It's all one huge green bar called sda1 (ntfs). What do I do next?
If I press install now, it says no root files system is defined. I tried the "shrink volume" function in Windows, but it complained telling me to run chkdsk, so I right clicked the c drive and nagivated to the chkdsk utility, told it to run on the next startup, which it didn't.
I am running Windows 7.
EDIT: I figured it out, see answer below