Trouble installing Ubuntu...

I suggest you use the 64bit OS as it will allow you to upgrade RAM easier later.

If you used wubi you can use the add/remove programs in Windows to remove it. You can also check it's all gone using this:

How do I manually uninstall Wubi?

Remove C:\ubuntu and C:\wubildr*

In Windows XP you need to edit C:\boot.ini and delete the Ubuntu/Wubi line. Alternatively you can modify the boot menu via Control Panel > System > Advanced > Startup and Recovery and pressing "Edit". For Windows 98 you have to edit C:\config.sys and remove the Wubi block. For Windows Vista/7, you can use the built-in bcdedit command or install EasyBCD to edit the boot menu. To use bcdedit, run cmd.exe as an administrator, then enter bcdedit to show all boot entries, note the {GUID} specified for the Ubuntu entry, and then remove it: bcdedit /delete {GUID}

To remove Wubi from the add/remove list, delete the registry key: HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall\Wubi

An easy method of removing this registry key is to paste the following text into a plain editor such as Notepad, close and save the file as something like removeWubiKey.reg (you may wish to go to Folder Options > View and disable the "Hide file extensions for known file types" option to check that the .reg extension has been applied correctly). Then you can perform the rest automatically by opening the file in the normal Windows manner, or choosing the "Merge" option from the right click context menu. Note: The formatting is rather strict, so copy the text exactly for best results. You may need to be logged in as the administrator to delete the key, depending on the version of Windows you are using. User Account Control in Vista may also ask for permission, in the typical fashion.

REGEDIT4

[-HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Wubi]
After deleting the registry key, Ubuntu may still appear in the program list. If this is the case, you may be asked if you would like to remove the item from the list.

Source:
https://wiki.ubuntu.com/WubiGuide