I am about to close this out, but I wanted to leave a final message for anyone else in the same predicament.
That will work in some cases for people who are having the same problem and have an applicable Mac. I don't have the link in front of me, but Apple has an official list of how new your Mac has to be to install a 64-bit operating system on with Boot Camp. They are the Macs starting in mid-2008 and on, if I remember correctly.
If you aren't using Boot Camp, then maybe you will have better luck, but I doubt it because there won't be any drivers. Apple won't have released any 64-bit drivers for your Mac. If you are persistent, then maybe, but I don't recommend trying unless you know what you are doing.
What I did to solve the problem, was simply install the 32-bit version. Because it's being used as a side OS, it doesn't really matter which bit-age it is unless you have more than 4 GB of RAM. In that case, only ~4 GB will be used.
Good luck.