Re: error installing
I'm not familiar with Wubi (the Windows installer for Ubuntu) so I don't know if there's a reason you're getting that error message. It looks like a bug, actually. Sorry, I don't know more about the error message you've been getting.
Generally, I recommend not using the Wubi installer as there are several limitations:
1. Limited size of the Ubuntu installation
2. Some slowdown in operation
3. It's a less-tested way of installing Ubuntu
4. If you want to remove Windows entirely, you need to use a complicated process to transfer the Ubuntu onto a real partition
5. If Windows stops working and won't boot, then you won't be able to get into Ubuntu either.
I recommend you burn the Ubuntu ISO to CD and then boot your computer from the CD. Select the "Try Ubuntu" option and then double-click the installer icon, or just select the "Install Ubuntu" option from the menu. Follow the prompts and install Ubuntu to a partition - you won't lose any data or Windows if you tell it to install side-by-side with Windows.
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.