Can I format my main partition and re-install windows 7 without losing the data on the second partition?

You should be able to do this. I’ve even created and formatted a partition before and then installed windows on the new partition (though i wouldn’t suggest this, as it can lead to some nasty errors, for obvious reasons). If windows doesn’t already allow you to do this by itself (and I would be really surprised if it didn’t, though it’s been awhile since I messed with partitions), you can use something like GParted, which you can burn to a live disk and use to wipe the partition before reinstallation. Just, you know, be sure before you wipe that you got the right partition. Though that holds in either case.

Be careful with this. The answer is not as simple as it seems. Either that or Toshiba are lying to me.
I had occasion to ask some techie from Toshiba if you could do this with their Toshiba Satellite Model A500D and I was told in no uncertain terms that you could not do it without completely wiping both the main drive and the partition. I am well aware – just so you know – of what a partition is here, so I’m not mistaking what was said to mean anything other than it would not be a good idea to try and wipe one and expect to still keep the other intact with data and all.
Now either that person was lying to me, or it could be model/manufacturer specific. There’s plenty to be careful about here. I’d double check with manufacturer websites where applicable.

Done it several times. You can and it’s actually very easy to find out how, intuitively, during the setup process.

@lightsourcetrickster That has never been an issue for me, so long as I don’t touch the Boot blocks. Once you alter those (say, installing LILO or GRUB) then things get… interesting

Just to finalize this question, I have successfully re-installed windows 7 without losing any information whatsoever on my Drive D:/. Thanks everyone.