Relocating Parallels virtual machines

I am constantly fighting to keep my 2014 MacBook Air’s 128GB SSD from filling. I use Dropbox to store files and don’t install many apps. However, I use Parallels with Windows 7 to run electrical certification software called EasyCert, which isn't available on OS X. Parallels seems to be using about 30GB. Could this be run from a 32GB SD card? The software is vital and needed every day, so messing it up is not a option. Otherwise, can I move some files/folders to the SD card and point Parallels to them? Rob Turnbull You can certainly run Parallels from an external storage device and, provided that EasyCert isn’t too demanding, maybe even a memory card. You don’t actually need to move Parallels itself; the bulk of the disk space is taken up by the Windows virtual machine. You can move this .pvm file off your hard disk to a new location and double-click it from there to launch Windows. Be prepared for a much longer boot time though. Even a fast class 10 SD card only has read times of 60 to 90MB/sec, compared with over 700MB/sec for your MacBook’s SSD. For only a little more, a USB hard drive such as the Samsung M3 1TB (£46 on Amazon at the moment) is much faster and roomier.