use the following steps :
1. First come on to your standby menu (by pressing red key)
2.Then hold the pencil key which is below the menu key.by pressing the pencil key switch off your mobile
3.After 3 to 4 sec switch on your n73 mobile by holding pencil key.
4.Now see how much ram would it freed by using "Y-task" software.
Plz dont ignore my answer I have solved my problem and I want to tell it to every n73 user.
plz remember me for a few second everyday when using mobile.
I am your friend and MY NAME IS A F.