want to change password but recovery mode doesn't show up the menu.

Ummm, that sounds like a windows installation screen. OEM = "Original Equipment Manufacturer". Not Ubuntu. You've booted into Windows OEM Recovery mode - the Windows recovery partition on the hard drive.

There's a chance you've borked the grub boot loader, since many of the OEM recovery programs re-write the MBR as soon as they are started and even before you tell it to start the installation. If that is the case you will need to re-install grub2 - look here:
https://help.ubuntu.com/community/WindowsDualBoot#Recovering_GRUB_after_reinstalling_Windows

The recovery mode that you wanted to boot into is the one immediately below the one that you use for a normal boot - ie probably the second line. It will have the linux kernel version as part of it's description. Anything that does _not_ have a kernel version number is probably Windows. If you are lucky enough to still be able to access the grub2 menu screen, select the correct kernel to boot in recovery mode and proceed as you were going to originally.

Chris

@chris
what is "borked"?

@dexter
what chris said, the blue screen is windoze

do you still get the dual boot screen? if you do, just select the linux recovery line. in some installations, the recovery line doesn't show up, so what you might be able to do is hold down the shift key while you're booting linux. this should show you another menu with a recovery line.

otherwise, just boot off your cd or usb drive and copy grub back to your hard drive.

incidently, you don't need to go into recovery mode if all you want to do is change your password. you can go to system>preferences>about me then click on the change password button on the top right corner of the popup.

the problem is that i don't know the previous password..is there a way to see the password???

@marcus --- borked -- http://www.urbandictionary.com/define.php?term=borked

@michael

not very on here speaks english with a high degree of fluency
borked is a slang term specific to certain regions

@dexter
if all you want to do is reset the password, just google "psychocat reset password" and follow the instructions in the link.

again, do you get a boot menu or not? if not, you have to reinstall grub.