Windows networking problems

I have 2 pcs at home connected by a switch to my cable modem.
I have to use dynamic ip on both machines to get internet access, but this means no network connection between the pcs over the switch. I can't even ping the other one.

The network works fine with a fixed ip on both machines.
How do I get network access between them with dynamic ip?

needs moar router (add a little nat + dhcpd)

sounds like your cable modem does not have a built-in router.  (if it does, you need to mess with configuring it)

couple solutions:
solution A:
 1. buy router or trade switch for router with built in 4 or 8 port switch, or buy cheap pc and configure as linux router (keep switch in this case)
 2. install router inbetween cable modem and switch
 3. hook pc's into switch, or lan ports on router
 4. configure router
 5. ???????
 6. profit

solution B:
 1. get 2 cheap ethernet cards
 2. install 1 in each pc
 3. get crossover cable (or maybe you can hook those up with standard ethernet cables to the switch too, it may work...), or if you plan to do this with more than 2 computers in future, obtain additional switch (not router)
 4. configure these extra network cards as fixed ip's on a different subnet than your cable modem
 5. do a whole bunch of weird configuring stuff to make windows networking work with this subnet
 6. ????????
 7. profit

solution A is recommended.

actually it should work with a switch if you're in the same subnet. but router is the better solution anyway.

Thanks for the replies. I'll experiment a bit with the switch, as I vaguely remember it working in the past.