Well, first of all... To use a Groovebox with a computer you need nothing more, only a Midi cable and a soundcard to connect the midi cable...!
But, Grooveboxes like the new ones from Roland are easy to use, switch them on and start playing around. You can use mostly of the grooveboxes as a stand alone machine and as a sound module. I own, just for phun, the Roland D2 with the whole MC505 soundset, great thing. I only use that machine as a sound module...! It rocks!
Maybe you should check out some Boxes from Roland and Yamaha at your music store...!
Frank