cannot add space to my installed partition in linux mint
 

originally i installed Linux mint to experiment with it and found that i like it more than windows, so i want to allocate more hard drive to it, i already have 400 GB allocated but i want to allocate 600 more GB since i have a large hard drive that i don't use. i installed GParted and was able to un-allocate 600 GB from my windows partition and now that's free and i cant extend my current 400 GB partition adding the 600 GB partition, if i was vague on my question just ask me.

You should not try to change partitions in a running system.

Boot Mint from the installation cd, if it allows you to run as a livecd. Then use Gparted to expand your Mint partition.

I don't think gparted will let you do some things to partitions (like grow them) if they are mounted (in use).

So, I suggest you:

1. Make backups of any important stuff
2. Make a careful note of which partition is which
3. Boot from a live CD (like the one you probably used to install mint), and run gparted from there.
4. You will want to grow your linux partition into the freespace, then you'll need to reboot.

Be careful, gparted is very powerful.
Good luck..