W7 Ultimate won't give you any benefits compared to W7 Home for fixing the broken settings.
Go to Control Panel > System and Security > System to see if you have 32 or 64 bit.
Put the DVD in the drive and double click setup.exe if it doesn't autorun. Click Install when you see the box.
You can do an In-place Upgrade installation which keeps files and personal settings, but I think resets the Network settings.
You can also do a clean install, if you prefer, by booting from the DVD, and formatting C: when you get the option.
You should back up any personal stuff first though because it will be erased.
If you have any problems, post back with exact error messages and details.