@PaulS: After looking at your number of posts i thought your statement would be helpful or useful. In return, it was just poor demonstration of failed irony. I think showing off is not a reason this forum was created for.
@lesto: Thanks for your interest in my problem. I went through the url you had given. I tried the "serial" in Process Explorer. Nothing found.
I don't have Microsoft ActiveSync on my computer too. The url's methods didn't help, but it was worth trying:)
lesto:
"port in use" is a Operative System fault, your PC didn't even tried to communicate with arduino. if the same problem is on the netbook, and the netbook has the c# program, then probably it doesn't shut down properly and so it doesn't remove lock on serial port.
C# Program closes serial connection every time it is closed itself. But it doesn't even matter, yesterday, before i wrote the post i had been trying to program Arduino on my brother's computer without this program even on disc space.
Tomorrow my friend will lend me his Arduino Uno. If an error appear while programming, that will mean it is the OS problem.