Connect one computer two to networks.

It appears that you only need the secondary router for its wired network ports: for your printer, network drive and maybe a server. With many popular routers (LinkSys, D-Link) you can put your primary router (Modem/Router) and your seconary router on the same network by using the same SSID, same encryption type and obviously the same encryption key on both routers.

The WAN port on your secondary router should be UNUSED. You will basically be bridging from your primary router to your secondary router over a wireless connection. You need to read the router documentation on what the exact settings are, but that's a supported configuration. I'd want to set up the subnet address and subnet mask on your secondary router to be the same as what's on your modem/router.

Personally, I've never used them this way. I had used a two-router setup like you but I run a CAT-5 wire between an Ethernet port on the primary router (the modem/router) and an Ethernet port (NOT the WAN port) on the secondary router. When I did that, my network card software showed two networks with the same SSID. I found it best if I set the channel on both routers to different non-overlapping channels (e.g. Channels 1 & 6, 6 & 11 or 1 & 11). It mattered when one of our laptop was at a place where it received an equal-strength signal from both wireless routers.

The reason I did that was to provide maximum available bandwidth for internet connection to any PCs connect to the secondary router as well as significantly faster file-transfer between PCs connected to either router by wire.

I've since replaced my secondary router with LinkSys PrintServer with a built-in 4-port switch.

Replace one of the routers with a switch, it'll put everyone on the same network. Otherwise if you can connect both networks to the computer that needs to bridge between the two, NIC (network cards) are pretty cheap these days. And that computer will get the best of both worlds.

If you need a router (or a set of network points in your second router), then you can convert your router to an access point instead, which will make it act like a switch and connection to your first router (if both routers support wireless). But I've found wireless to be inconsistant sometimes.

No, you will need a router. The modems only function is to provide an internet connection, not a network connection. I'm not sure what you mean by "wireless card" on the laptop. Another wireless modem? Or a wireless network card? If its a wireless network card in the laptop, then you will have to get a wireless network card for the desktop also. Then a wireless router to connect the two computers together.

Why not have ONE router connected to the internet? Connect all devices through this router, using a network switch and wired lines where you now have wired lines. There is no value in 2 routers.

This puts all devices on a common subnet and enables sharing as desired.

A hint on the topography would be useful. Sounds like you could have all the kit in the same room and not have a problem with a 3ft thernet cable. Failing that a cheapo PC with 2 NICs acting as a bridge would do.

If both routers are wireless, make them part of the same network, Same SSID, same encryption key, etc etc.

You should be able to connect to them at the same time wirelessly. Check your settings, something seems to be stopping you.