I would suggest installing Ubuntu into a Windows directory (creates an "ubuntu" directory). The performance degradation is not significant - the code runs native and uses "virtual disks". Unless there was something special in 11.04, I would have recommended going with 10.04 (an LTS) until 12.04 (an LTS) becomes available. You can upgrade directly from LTS to LTS. If you ran with 11.04, skipping 11.10 and then wanted to upgrade to 12.04, you would have to upgrade to 11.10 before moving to 12.04 (or re-install). The other advantage is removal of Ubuntu is like any other Windows app uninstall (there is an uninstall file the ubuntu directory). Since you said you basically wanted a "quick boot" to connect to the internet, this is a lot easier than partitioning and creating multiple boots. Also, it shouldn't interfere with the MBR. In an XP system, it adds a couple of files to the "root" (C:) disk and adds a line to the Windows boot.ini file (to boot into Ubuntu code). I am not sure of the process for Vista and Win. 7 (and in the case of dual booting).