RafaelLopez: That is, if you're running very basic applications, or even just pure DOSBox. For a game that asked for 16MB RAM back in the days (say, Duke Nukem or Ultima VII), you do need a lot more than 100MB RAM to play decently (I can't tell the exact amount though).
Edit: and yes, I'm talking Windows, this might definitely differ on different systems.
Edit 2: wait a second, what the hell, did I just try to tell Qbix about DOSBox?! O.o You should throw a shoe at me for assuming to know more than you! But seriously, based on personal experience, 100MB RAM is totally out of the question here...although I know DOSBox feeds on CPU power.
Just tried Duke Nukem 3D, on a Dell D600 with WinXP SP3, 512mb ram, 1.6ghz and 32mb graphics [...] Memory usage, according to the task manager was at around 70mb and cpu load between 40% and 88%.