You should just be able to format the partition in question, and re-install windows on that. If all your data is on other partitions, leave those alone and you're good.
As far as I can remember, Windows asks you which partitions you want to re-format during an install. The are also several live CDs with graphical tools that will let you edit and reformat ...
Yes, this is possible, depending on how much free space you have left. If you have little free space left, it is still possible but becomes very cumbersome. Given that you have ommitted how much of the 1TB is still free space, I will assume you have plenty of space available.
You first want to open Disk Management. This can be accessed by right-clicking the ...
On 64 bit Windows 7 you can install and use Virtual PC to run a 32 bit instance of Windows in a VM. This will be a genuine 32 bit OS and browsers will announce themselves as such. This may be overkill to solve your problem but it is one route.
See Will running Windows 32-bit virtual machine on 64-bit Windows 7 fix this issue? for a similar question.
Websites dont know the architecture you are running - they infer it from the UserAgent atring sent by your browser.
A solution is to get a plugin for your browser which allows you to set an alternative useragent string which reflects as coming from a 32 bit browser. They are fairly easy to find.