When you allowed Mint 12 to install alongside Windows, what has happened - very likely - are two things:
About uninstalling Mint 12 (or any other operating system):
- As one step of the installation, GParted will have divided the 10 GB area into 2 partitions: first partition of 7.5 GB for the Mint 12 operating system and the software and second partition of 2.5 GB as the Linux swap area.
This is perfectly all right. Every Linux installation will need a swap partition. The size of the swap partition depends on the size of the RAM.
The first partition holding Mint 12 and the software which comes with Mint 12 will be an Ext4 filesystem very likely. Again, this is perfectly all right. Linux can use NTFS and FAT32 filesystems, but it is no good idea to try and install Linux itself on a non-Linux filesystem. So Ext4 is perfectly all right.
- As you simply allowed Mint 12 to install alongside Windows without having a look at the details of what it was going to do during the installation, Mint 12 will have written its bootloader Grub2 into the master boot record of your disk. This is not really what should have happened, because Grub2 will have overwritten the Windows XP bootloader this way. - Yet, this is a solvable problem. So do not despair, yet.
As a rule, there is no need to uninstall an operating system. You boot the machine using a live DVD (Windows or Linux) and simply delete exactly those partitions used by the OS that you wish to get rid off.About repairing the existing Windows installation:
I may have missed the statement, yet, as far as I understand you can currently not boot into Windows XP. If this is true, then this supports my assumption that the Windows bootloader has been replaced by the Mint 12 bootloader Grub2.
In case you have got the original Windows XP installation DVD, you should be able to boot from this DVD and run a command prompt and at the command prompt execute the commandline "fixmbr". fixmbr should restore the original Windows bootloader.
Afterwards you should be able to boot to Windows XP, but no longer to Mint 12, because fixmbr will have removed Grub from the MBR. In your case this is no real problem, because you are going to remove and reinstall Mint 12 from the scratch anyway.
In case you do not have the full Windows XP installation DVD - quite common vice today, selling Windows pre-installed without providing the original installation medium to the customer
- you might also use a self-created Windows rescue DVD/CD provided you have created one. The manuals strongly recommend to do so. Yet, I am afraid hardly anybody cares to do so.About using EasyBCD to repair the existing Windows installation:
So, in case you do not have the original Windows XP installation DVD or a Windows XP rescue CD/DVD, there might be a chance of repairing the exisiting Windows installation with the help of EasyBCD, as has been recommended by K7plus1.
Yet, I cannot offer any help on the exact steps: I am sitting at my Windows 7 / Ubuntu 10.04 dual-boot netbook. No external media which could be used for booting and testing anything available here at the time of writing this. And I do not know EasyBCD well enough to offer advice on its usage without trying myself beforehand.
So it may be wise to wait for K7plus1 and hope he can help with the EasyBCD usage problem.
About your complaint that not too many people had bothered to offer their help in your thread: Well, this is a general problem in a lot of forums, and this forum sadly is affected by this problem as well. There are more users seeking help than there are users who can offer help.
Modified some phrases after having noticed that you have got Windows XP, not Window 7.