using both Tiger and Windows

I'm new to the whole boot camp thing, running windows and OSX on one machine. How does it all work? If a virus would be to get through my firewalls on the windows partition, would that ruin the OSX side of the hard drive? Please let me know of everything i need to know. Thanks!

Virus' won't affect OSX. Due to Windows not reading or writing to the OSX partition. Even if you had MacDrive installed the Virus would not work in OSX. Only Windows.
A virus for windows is just that, a virus for windows.

although.. there are exceptions like a dodgy macro in a spreadsheet, but then that's limited harm and you have the choice to run macro's.

Virus' wont harm the EFI(boot section of the HDD) as Bootcamp emulates a BIOS procedure to allow Windows to operate. So even if you got badly infected you can still boot to OSX as the EFI partition wont have been accessed due to the different type of format the EFI is in.