a 2.5" HD will slot right into the machine anything bigger than 80Mb will do...
You could consider an `accelerator` that will allow you to increase the memory.
The internet is full of PD to download...just use google.com
I used to run an 1200 off just one floppy, but you really need all the disks, try to get at least 3.0
You can then install them onto your new Hard-drive...
:-D
