Equipping your PC with a firewall and antivirus tool may keep out most hackers, but doesn't guarantee your security. If someone gets physical access to your system (it's stolen, say, or a computer repair technician is snooping around) then the best "internet security suite" will be no use at all, and there's only one way to ensure you're protected: encryption.
Comodo Disk Encryption can help in a couple of ways. The simplest option is to create a virtual encrypted drive that will hold your most confidential files. This works just like any other drive - you can see it in Explorer, drag and drop files there, save documents to it from applications - but it's actually just an encrypted file, managed by Comodo Disk Encryption. Unmount the drive and it disappears from view: snoopers will never know it was there, and even if they do spot the drive, can't access it without entering your password.
Alternatively, if you're after industrial-strength security then you can have the program encrypt your entire partition. Comodo Disk Encryption then won't even let your system start until you've entered the password, and you can optionally require authentication with a USB memory key, as well.
This more heavy-duty approach is effective, but can lock you out if things go wrong. Fortunately Comodo understand this and provide tools to help. So you can create a backup copy of your USB key, for instance. And a Rescue Boot CD will restore the Comodo Disk Encryption boot loader if it's corrupted, a problem that would otherwise prevent you starting the PC.