In many cases when an anti-virus or anti-malware program finds malicious files, they are renamed and moved to quarantine or another designated location (by the vendor) so they are rendered harmless. However, if you are using other security scanners they may detect these files as a threat. In other cases, as boopme noted, vendor-specific definitions/signatures files may be detected as threats by other security scanners.
According to a Moderator at the PC Tools forums, .vbt files are randomly named temp files created by their program's scanner. ThreatFire (also by PC Tools) users have reported similar detections by other scanners when encountering .vbt files.
If you suspect a detection was a "false positive
", then you should submit a sample to the vendor so they can investigate and take corrective action. Please refer to How to submit virus or potential false positive samples to ESET's labs