3.321 and 4.08 "Dual Install"?

[Deeter]

I am running 3.321 on my laptop, a Sony Vaio Core 2 Duo 1.66GHz with 2 gigs RAM and Vista Home. It runs flawlessly- never had a problem with the system or software at all. I am thinking of upgrading to 4.08 Hoster, but am reluctant to do so if it requires removing 3.321 (which I know works). Can I purchase and install 4.08 and try it out without uninstalling 3.321 or do they use some of the same files/folders? Will 4.08 "change" any of my 3.321 files so that they are not backward-compatible? I'd really like to have access the new features but I don't want to give up the stability I have with 3.321.