Is there a difference between wubi install and doing an install of Ubuntu alongside windows7? I ask because I used wubi, but I'm having trouble with certain things like being unable to change my brightness settings and I'm wondering if installing from a usb drive would change anything. Also, I've tried to do a usb drive install, but it doesn't give me the option to install alongside, it only shows the "Replace Windows 7" and "something else" options. Is this because I already did a wubi install?
The difference between a Wubi install and a Dual boot is that with a dual boot Ubuntu has its own partition while with Wubi the Ubuntu drive is actually a file on Windows. I doubt that changing from Wubi to dual boot will make any difference to brightness settings however.
That said a dual boot is preferable to Wubi for the following reasons
I would always install Ubuntu separately either on its own machine or dual boot but since you already have it working with Wubi I doubt you would notice any significant improvement by re-installing.
If you do decide to reinstall: remove your Wubi Ubuntu first using the control panel in Windows. This will free up some space ready for the installer to re-partition the drive. Also make sure you have good backups of both Windows and your personal files in Ubuntu. It's rare for the install process to go wrong but people have lost everything in the past. Finally make sure you read every question from the installer carefully. Ubuntu will happily install side by side with Windows but the same installer will also happily wipe Windows from your machine if you tell it to.
A Wubi install is the same as a normal dual boot, except for a few key differences - it uses a virtual disk and it boots differently. Brightness settings will not act any differently.
When you install from a CD or USB it does not detect the Wubi install, and it makes no difference to what the installer sees. If it only offers to replace Windows7 it probably means you have used 4 primary partitions already - the maximum on an disk with a MBR partition table. Some computers are shipped with all 4 primary partitions already allocated e.g. HP computers. You best option then is to backup the contents and then delete one of these partitions.
From the Wubi install you can go to a terminal and run