Even using Netscape mail if you open the attachment it will infect your system. Since you're not an Outlook user the virus can't send itself to people in your address book BUT the virus installs a backdoor which sends your IP address to the author and may allow the author to "control" your PC right down to formatting your hard drive.
Also note: A keystroke registry which will watch for passwords, credit cards numbers, etc. entered at the keyboard is installed and can send this info out over your web connection.
If you don't have virus protection regularly updated you're playing ruskie roulette.
You can get McAfee for 29.95 (Virus Scan) and updates are free via the web.
Symantec - Norton AntiVirus allows a year of "free" updates but then you have to pay for updates - which last time I looked were "3.950" per year. Frankly, I suspect its 39.50 a year as $3.95 annually seems hardly worth the processing costs - anyone want to help out?