7.6v2 will not run right on x64 Windows..... You "might" get it to work somewhat using 32 bit emulation but it's not likely. Some have had slightly better luck with 8.0/8.1 on x64. 8.5/8.6 was the first version of Flexi "officially" supported on x64. You will also have to make sure you have x64 drivers for your machines (printer and cutter) as well. Ultimately if you are not planning on either finding a used copy of Flexi 8.5 or higher (or upgrading to the newest version 11 "Cloud") and making certain that your machines have x64 drivers I'd personally suggest not trying to mess with 64 bit. Your only official upgrade you can get for your 7.6 version is all the way to the newest cloud version, once they release a new full version they discontinue allowing upgrades to other lower versions - in other words you cannot upgrade your 7.6v2 to 8.6v2 or 10.1, etc, only to the newest version.
8.6v2 (or 8.5 which can be freely updated to 8.6v2), if you can find it is next to 7.6v2 probably the most stable and best running version of Flexi I have seen. We ran (and still do) 8.6v2 for a few years but we also have the newest cloud version now too and are transitioning over to it. 64 bit can make a pretty big difference although I don't believe Flexi (even the newest cloud version) is a true through and through native 64 bit application. 64 bit will however allow you to have greater than 4GB of ram and if you have other native 64 bit applications like Photoshop CS5 and Illustrator CS6 they will get a rather large performance boost on 64 bit with over 4gb of ram.