best way of moving files to a DOS machine?

For a permanent solution your best bet is getting the NIC working. You'll need DOS drivers for the NIC. Check 3com's website to see if they still have them for your model.

If you're connecting directly to your Vista machine, you'll need a crossover cable (pins 1,2,4 and 6 are swapped). You can buy one or make one. If your using a hub or switch, a standard cat5 cable will do.

The various ways of adding networking to a DOS machine are too numerous to discuss here but here are a few links that will get you started:

http://www.dendarii.co.uk/FAQs/dos-net.html

http://bbright.tripod.com/information/dosnetwork.htm

http://www.freedos.org/freedos/news/technote/157.html

If you succeed in getting TCP/IP running you'll have the benefit of being able to run a TUI web browser such as Lynx so you can download files directly to your DOS machine.

If you want to keep that DOS machine going indefinitely, this might be a good thing to have:

You can buy it here: Tiger Direct - ($19.99) Sabrent 1.44MB External USB 2X Floppy Disk Drive

...and hook it up to your Vista system (or any other system, too).

Then you can create new floppies, move files back and forth easily, keep backups (on your Vista system), and get more DOS files/games from the Internet (via your Vista system).

If this is a one-time need (i.e. you do not add games ofter), then the easiest way may be to remove the hard drive from the dos box and attach it to your Vista machine via a USB adapter (assuming your Vista machine does not have a free IDE connector). Dump the files down the line then return it to your Dos machine.

Be careful not to format the drive when Vista sees it for the first time.

One way of moving files to old machines that I have found useful is to use ZModem. It's not just for dialup connections. If you setup a RS-232 cable from a reasonably new computer, you can use HyperTerminal on Windows to send files by ZModem or similar serial transfer protocol to the old computer, which can surely run Minicom. The only problem is getting minicom to the computer - you'll still have to do that via floppys.

If your newer computer doesn't have a serial port, you can find one (we use these ones) pretty cheap.