I've seen this happen with certain software installations - if I remember correctly, at least one version of Autocad inserted lots of blank spaces into the add / remove program dialogue. Does this happen before you install software?

Thanks for your advise, you are right, as today I've seen same problem on sony Vaio, which i have installed 02 new programms as follows:
1) Microsoft Atlas encarta 2000 (full on hard drive)
2) Energy Blue Theme (which i've downloaded from net)
so the next step is to find out which one them causes the problem.
appreciate your intrest for advising and wish you the best.
Regards / Salaee

Glad you've narrowed it down - good luck with finding a solution - post back when you find the culprit!

Good day,
Finally found out the problem was due to Encarta program, which contains research organizer, so after removing and installing one more time (without R/organizer), every thing goes well.
Thanks again for your intrest.