Crashed Mint installation, reinstall

[nmr472]

I successfully installed Mint 14 alongside Vista on my Lenovo Dual Core R61. It worked fine

Yesterday I had a crash due to the battery running out. Now Mint won't boot from the sda option in the boot dialogue screen.

I think I need to reintall Mint, but when I go to install it it says there are "multiple" operating systems and asks me if I want to install Mint alongside all of them. When I installed it originally it just asked whether I wanted to install alongside Windows. I'm running out of disk space (500GB disk) and want to know which of the disk partitions I can delete to reinstall Mint. my partition sizes look like:

Free space 5658MB
/dev/sda2 ntfs 301879 MB and 217741 MB used
/dev/sda7 ext4 86564 MB and 71411 MB used
/dev/sda5 ext4 102794 MB and 49041 MB used
/dev/sda6 swap 3208MB and 0 MB used

I have 3GB RAM

Can I delete the ext 4 partitions to make space for the new Linux install?
I want to keep the Windows option for a while until I'm sure I won't crash again and lose all my data.
I don't have a 500GB back up drive to privide protection.

[RodMyers]

You should be able to overwrite the / and keep the /home directories