As you have said, you have both win 7 and Mint 11 dual boot. In such case generally people manually store data on NTFS partition, since Linux can read / write it. (Hope you have only one hard disk.) If so, it is easy, you can backup data to any external device through win7.
Incase you have some data in /home folder which is partitioned ext3 or ext4, you can use LIVE CD, just boot into LIVE CD and backup all the data you need it. For future ref, there is a free service called Dropbox, which allows you to upload upto 2 GB data for Free. You can consider this service, if yuou have a broadband.
If you have enabled sync option in Opera, FF or Chrome, then no need to worry
Through LIVE CD, you can check weather everything is running fine or not, then proceed to install. Fresh install takes 10-15 mins and troubleshooting may need from 5 mins to 30 mins (or even more), depending upon problem and your expertise.
Since experienced users have suggested you to go for fresh install, I will try my best to explain manual installation:
It is not difficult as it looks like. Once you are able to do it, it will give you much confidence. Alternatively, you can try to install inside Virtualbox. I suggest you to try to install inside Virtualbox, if you have never installed any other Linux manually
i.e. the current install, that you managed and messed up
is your first Linux Install. Virtualbox can be installed inside win7 (~95 MB exe file). This will give you good confidence. (Search in net on how to install Linux Mint as guest OS inside Virtualbox, if you do not get required results, which is unlikely, replace Mint with Ubuntu.). Next time, whatever R & D, you wish to do, do it inside Virtualbox.
To explain installation with screen-shots is beyond my pay grade
Linux needs 3 partitions as against only 1 partition that windows require. Other partition is automatically created for backup.1. /root partition:
This is where you system is installed2. /home partition:
this is where all data and maybe config files are stored (please correct if I am wrong). So I case of multiple distros like one windows and 2 Linux e.g. Mint and Ubuntu, you can have a common /home folder.3. /swap partition:
This is like RAM. It is generally 2x times the size of RAM. If your RAM is 2GB, then Swap partition should be 4GB.
If you again select dual boot, as I did in case of Ubuntu 9.1, another copy of Mint can be installed along with existing one.
After you select manual install, you will have to create / select partitions.
Since you have installed Mint, so all three partitions would already be present.
Select, the partition, in which MINT is installed and just reformat (only) this partition, keeping same file system i.e. ext3 or ext4 (It should be ext4, but even ext3 is of no harm).For Reformatting, Gparted will be triggered. You need to right click on the partition and select option to reformat to ext3/ext4). After selecting, click apply button (on main menu - just hover over it to read tool tip
) to start the format process. (search for manual install and you will get good explanation along with screenshots).After the format is complete, you will be returned to the installation screen where you need to select other partitions.
In your case, SWAP should be automatically selected, if not, you can easily identify SWAP, as it is the smallest partition between 1 GB to 4 - 6 GB.
Just select it without formatting.
Then select the last, remaining partition as /home and format it. This will clean all data and config files, etc. If you do not format this partition, still you will be able to install Mint.
After selecting and formatting all 3 partitions, just follow the instructions and let the install do it's work.
In 10 -15 mins, you should have Mint installed, ready to use.
-- Note: You can also install win 7 as guest OS inside Virtualbox
Tip: If you want to do any R & D after you install Mint (which is host OS), Install Virtualbox inside Mint and then Install Mint (as guest OS) inside Virtualbox. Tip2: Store data mp3 on NTFS, so that you can access through win 7 or Mint. I have common drive for data since 2 years.Till now, I have encountered any data loss