Your laptop supports 64-bit operating systems but there would be no point in upgrading unless you wanted to have 4 GB of memory or more. Your laptop comes with 3 GB if I'm not mistaken.
Any external hard drive should work fine on a 32-bit operating system, doesn't matter what it is for, video editing or otherwise.
And just to dispel any possible confusion, there is no such thing as a 48-bit operating system.