Different ver. of CA Anti-virus yields 2 different results

[Happy Hopping]

I have a laptop running XP Pro, running CA Security Suite, and I use that to test scan virus. So now I have a program that I transferred to this laptop to scan for virus, and it found nothing.

Back here in my desktop, running Win 7, running CA Security Suite Plus, which really is the same signature file, except this ver. run under Win 7, found a malware called:

Win32/FakeAV.ZAAA! suspicious

So who's right? And how can this be? I have been using this brand name for many years, I know they only have 1 signature within the co.