Rogue:W32/XPAntivirus.gen! is the Generic Detection for Rogue:W32/XPAntivirus
XPAntivirus is a family of rogue security programs that claim to detect and remove malicious software, but give fake and exaggerated scan results in an attempt to trick people into purchasing the program.
About Generic Detections
Unlike more traditional detections (also known as signatures or single-file detections) a Generic Detection does not identify a unique or individual malicious program. Instead, a Generic Detection looks for broadly applicable code or behavior characteristics that indicate a file as potentially malicious, so that a single Generic Detection can efficiently identify dozens, or even hundreds of malware.
For more information about Generic Detections, see the Generic Detection