I wouldn't really count on HL2 working on a 16Mb card - I have a 128Mb card, but seeing as it is a Nvidia, it can't handle HL2 at full res - the card you have probably wont cut it for recent games like HL2 or Doom 3 etc that all require cards that support DirectX 9.
My suggestion would be to get a new card anyway, but if you are not too keen on spending some cash, then there are always cool games around that are worth playing that will run on your system... just got to find them =)