"lost focus to explorer.exe - My computer"

I have strange problem , "My computer" pops up all the time , when I watch video on full screen then the Media Player notice :
"lost focus to explorer.exe - My computer"
at start i post a thread at Malware Removal forum , but after reading more I dont think its Malware problem.
I cant even write things on Word or do works because it pop up all the time,
when I close "My Computer" , it opens again - non stop.

the post from Malware Removal
http://forums.majorgeeks.com/showthread.php?p=1090394#post1090394

I used TweakUI to try and fix it - nothing help
I have last windows updates, last drivers. Windows XP pro SP2 , amd 64 - good computer.
This problem started , I think , when my little brother opened a file even when antivirus didnt accept that file.

please help me :cry

 

SOS :wave

 

yea , I tried and tried even more programs , nothing help , any idea?