I have two HDDs, 80Gb each. On the first HDD, I have windows 7, on the second HDD, I've installed Ubuntu, but I don't understand why can't I use Ubuntu.
When I restart my PC, it doesn't ask me about Windows 7 or Ubuntu, Windows 7 simply starts.
Note: When I've intalled Ubuntu I picked the second option "Erase disk and install Ubuntu", because the first option did't let me install Ubuntu on the second HDD, only on the first one.