Linksys WRT54G and Firewall software

Hello.

I'm using a Linksys WRT54G with one wired PC and one wireless laptop. Do I
need to run firewall software also? I had been using EZ Armor FW and Virus,
but the desktop slowed to a crawl. After removing the firewall software
(accidently), it runs normally again. This PC isn't exactly a powerhouse,
but it's OK for my needs.

How bad is it (and how dumb am I) if I don't re-install the software FW? Do
I really need it, seeing as how both PCs are running behind the router?

Thanks, from an obvious amateur.


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