Router - Mac to PC - safe?

I use an iMac G5 and upto now this was the only computer in our house. So I never needed any anti-virus software or anything.

But now we've been given an oldish PC, and have connected it to the internet using a router from my modem. Is there anything I need to have installed to protect my mac, you hear about how people crack into other peoples routers and steal their internet use or details/files.

I know macs don't really need software the anti-virus software but now that a PC is somewhat connected to it, I don't know if anything has changed or not.

Can someone give me advice on what is needed if anything?

Also the person who installed the router said I should be running an anti virus program on my iMac as they aren't as safe as what people make them out to be. I told him that they were still pretty much safe against viruses but he kept insisting they weren't, and they are always being infected or hacked into.

Any help would be greatly appreciated.
Thanks!

 

cool, just what I needed to hear. Thanks
The PC has the AVG program on and maybe something else too

 

I had some problems with my connection yesterday and had to ring up Blueyonder (Virgin). I don't know if it was because I had put the router on the previous day or because some phones etc around this area were experiencing difficulties. Virgin told me to unplug the router as they couldn't help with that in, tested my modem and its working fine now.

Also someone I know said to keep any wires away from the router as it may interfere with it

 

think I might have to take it back, it just won't let me online if that is connected