Working on my CCNP Rack! Need help.

I justed purchased the following:

1 Cisco 2621 64 Ram and 32 Flash Memory.
2 Cisco 2610xm 96 Ram and 32 Flash Memory.
1 Catalyst 3550 24PWR

The question I have is about the 2621. Since I have 32 of flash
installed, what is the latest IOS that can be installed?

I know for a fact that I could fit the 12.4 Releases of the IOS, but is it
supported? Will it install properly?

Thanks for all the help!
Sorry to be a newbie.