Thank you all for your replies.
I've tried a system restore, but it didn't solve the problem. Also, as EzioAuditore suggested, I've turned off and on explorer.exe and ran the SCANNOW command, but both didn't help as well.
And yes, only the icons in the taskbar and the desktop have been changed, not in the systray, and as I live in Israel I type from right to left, and as Hebrew is read and written from right to left the systray is on the left and the start button on the right, as some of you have already noticed.
Any other solutions?
And Kaktussoft, what exactly did you do by right-clicking the desktop?