In response to your first question, are you absolutely sure your HD has failed? You may be able to get it back after FDISK and FORMATting it from a DOS prompt using a boot disk. Although the file structure will be trashed, the hardware might not be. If you do recover from this, I wouldn't rely on the drive - just use it for archives.

As to the second question, in theory it must be possible, but in practice highly unlikely. It would be fairly easy when you're sat in front of a PC you want to break, but doing so with a virus or remotely would be difficult.

I wouldn't not use a firewall , though, in addition to a good virus software. I've recently bought Norton Internet Security Pro which includes a copy of Antivirus pro, which you could get as an update from their online store - and no, I don't work for them

Hope it all gets sorted,

Pete