I am concerned I may have a virus (possibly a variation of the Windows Security Center malware). When I clicked a link, a window popped open and started downloading something. I immediately closed the browser, but not before a window popped open that appears similar to what the Windows Security Center malware shows. Later the same day, I received a phone call that, based on internet research, was definitely associated with the Windows Security Center scam ("hello, I am with Microsoft and we noted you have lots of unusual activity on your computer"). This generated a lot of alarm - hopefully the events are coincidental, but I want to make sure my computer has not been compromised.
I contacted Symantec via chat and was advised to download and run Norton Power Eraser. It found nothing. The technician then advised I download and run NBRT. I was successful in downloading, and created a boot disk on USB. When I ran it initially, it appeared to run correctly, gave the "scan" option, but would only scan my external backup hard drive. I disconnected the external drive and tried to boot from the USB. This time, it starts correctly, gives the yellow screen, but then goes into regular startup and boots like normal. I have repeated this several times and it will never start from the bootable disk. The Symantec technician indicated there was nothing further they could do and that I probably have a virus. The strange thing is, there are no signs of a virus being present (i.e. no pop-ups, machine appears to be operating correctly)
Should I be concerned because NBRT will not work on this computer? Does that imply I have a virus? Suggested next steps?