O Roff of all Knowledge - PC security question

I left the PC on, unattended, while watching MotD. When I came to switch it off, I found that I had no firewall or AV icons in my system tray, and there was a skull + crossbones in the middle of my taskbar. After a couple of exploratory clicks, I did a hard reboot, into safe mode, and ran Avast Scan, Spybot scan and Malwarebytes scan, deleting only a couple of trojans, nothing too menacing.

I then restarted again, and ran the same scans, fully updated now, in normal mode - and found nowt. There aren't any passwords stored in my computer, nor any that FF remembers for me. I'm about to do some Xmas shopping online: am I safe to continue, or is there something else I should do first?

Is it likely that someone's left a bot on my puter somewhere that's waiting for the next time I enter my card details?

Ta in advance

Suggers

Posted By: Sugbad The Bad, Dec 4, 12:27:49