Win 98SE Wireless Woes

Hello all:
I seem to have become a one-person IT Dept. for our office. We have an office LAN with six computers (Dell Dimension Celerons - Win98SE) wired into a server shared with the boss's son's local ISP, however we do NOT have internet access (long story).

As a work-around, I have suggested a dedicated Verizon DSL line (Westell 6100 modem) connected to a Linksys WRT54G (v.5) router. One person has a new Dell Inspiron w/WinXP that connected wirelessly without a problem. However, all attempts to utilize a wireless USB adapter on the Dell Dimension desktop have failed.

Tried Linksys WUSB54G - 1st try: Installed, connected to network, unable to connect to Internet. Restarted, unable to locate adapter; restarted again, unknown device.

Substituted Belkin USB adapter F5D6050 (802.11b). Installed, connected to network (router sees adapter, adapter sees router), unable to connect to Internet (DNS error). At command prompt, am able to ping web address by URL or name; in Windows, DNS error.

Have updated firmware on router and adapter; have installed Firefox as alternate browser without success. Have disabled WEP, no luck. Tried setting up e-mail account through Outlook Express and Verizon - no good.

Cannot use internal NIC card, as causes conflict with office LAN. Unplugged office LAN to confirm that wireless adapter was being used by browser.

Any ideas short of reformat/clean install would be greatly appreciated.