i know i've asked alot of help last day
the wpmu installation went so fine .. firstly i found an error in signing up page which drmike fixed it
but after fixing it and on the 2nd page of registeration i found this error:
Warning: in_array(): Wrong datatype for second argument in /blablabla"""/wp-includes/wpmu-functions.php on line 881
i wish anyone can help in this .. drmike did alot of help here and i don't want to bother him more