I've rarely had an issue with running software for 32 bit on my Vista or Win 7 install. The main barrier is how much RAM you have. You can check with Speccy (Look at the amount of RAM. I'd do a screenie but I'm on my netbook which just boots Linux).

I'd go with the 64 bit if you're going to be using it for a while (another 18 months or so). Otherwise you may as well stick with the 32. IMPORTANT: If you do go with 64 bit and there's the option to get 64 bit software from [insert vendor here], DO SO