Infected Or Not?

Hi...I have a problem...or at least think i have a problem

I run windows xp..sp2 i believe

2 weeks ago i was offered the new version of WMP to bring it up to ver 11

i accepted

since then it seems that every half hour or so...sometimes more frequent

I have a dialog box appear and then disappear

it's like a program's running, but there's no information on the bar...it's hardly open on the task bar for more than 3 seconds and when clicked it immediately disappears

I have the latest update from NOD and it doesn't find anything
I haven't found anything with spybot
nor AVG....

I have Windows task manager all programs that run have a time stamp (Most)

and i never find the program that runs at the times that i see the program run

all potentially dangerous programs have been checked out

what's the next step?

thanks in advance

 

Hello,
You were offered to download - where?
Mrk