Using Gparted (not the Mint Installer), unlock and delete sda5 and sda6.
2) Create a partition for swap of at least 1GB and format as Swap. If you plan on using hibernate make it 2x the amount of RAM installed in your computer.
3) Create a 20GB partition and format as ext4
4) Create a 30GB partition and format as ext4, then click the checkmark to apply all changes.
You can make your /home partion bigger if you want to. I just made it so you have room for another Linux install if you want to.
5) Run the Mint Installer and choose manual partitioning
6) Select the 20GB partition, click edit, and choose / (root) as the mount point
7) Select the 30GB partition and choose /home as the mount point
Then Foward your way out of there and continue with the install.
Ignore any warnings about not formatting, you already did that.
P5N-E SLI, Core2Duo E6850 3GHZ X 2
2 GB DDR2 800MHZ
EVGA 8800GTS 320MB
Arctic Cooling Freezer 7 Pro