If you want to run from dos all you need is mame compiled for dos. The last official version of dos mame that came out was .91 which isn't to bad. Here is the link for the pentium optimized version.
http://www.mame.net/zips/mame091b_dos_i686.zipHere is for the non optimized version for use with AMD's or the like
http://www.mame.net/zips/mame091b_dos.zipThen you just need to find a front end that supports dos and set it up pointing it to your dos mame version. After that edit your autoexec.bat and have it run your front end. This is of course very simplified and if you dont know how to mess with dos its will take you a little while
I just started setting up my cocktail cab to run in dos and it was much harder than I thought it would be. My original load time for a game was like 3+ minutes after a bunch of suggestions and playing with it I got it down to about 13 seconds but that took a decent amount of time. I dont even have a sound card setup which could be very hard depending on your soundcard/mobo.
Just dont go into this thinking you can get a nice dos setup running as quick as you would get a windows setup running. Stuff like getting the soundcard working and getting nice and quick load times on your games could take a little bit of work. And if you dont have any dos experience it will be all the more difficult.
With that being said I think running DOS should work well for you. You have a older system so without windows running in the backgroud games will run faster also there wont be that slowdown after you have switched between a couple games. And of course not seeing that windows bootup screen is always nice.
Here is the thread I started about my extremely long loading time maybe it can help you get started.
http://forum.arcadecontrols.com/index.php/topic,33963.0.htmlAlso here is a simple getting started page. You will probably want some different setting than this but its a decent start.
http://www.mameworld.net/dosmame/And one last thing the links I posted up top are the newest version of mame since you are running older hardware you might consider running an older version to decrease load times and increase speed. If you want to dowload and older version just change to link to what ever version you want. A lot of people running just the classics run something like version .33 or .35 and some people run versions from the .70's or .80's so they can play newer games but without all the new bells and whistles.