1) Roland MDX-15/20 Basic Updates
Rolands come in all kinds of condition, but most need these steps.
Get some adhesive backed LED strip lights and line the attache them to the inner wall so you can see the tool head for changes and to inspect cut quality.
firmware and software
Use the serial number off the back and go here http://www.rolanddga.com/owners/support/ Go to the self help.
Get the "Full Version of Modela Player 4 v2.0"
Download the firmware if needed (likely).
USB to serial adaptor
Roland recommends the JU-CB1S12-S3. Key items are 1) supported by your flavor of OS and, 2) supports RTS/CTS, DSR/DTR. Once installed make sure to turn on HARDWARE HANDSHAKING.... fail this step and you will have random cutting. I've been using a Insignia™ - 1.3' USB-to-RS-232 (DB9) PDA/Serial Adapter Cable from best buy and a 9 to 25 adaptor.
disable the safety
jam a piece of pcb or paper wad in the little switch at the front, or make a fancy light curtain with lazors.
If it didn't come with a power supply, an old HP laptop 19V (might work to 24V with adjuster turned down to 20V) 2+ amp supply from the cruft bin will do. Center positive, 3mm jack.
The cables can be loose or come unspooled. As long as they not frayed and have both ends they are good. Look here if routing them is an issue.