If the standard password 00000000 (8 Zeros) Doesn't work and you can't guess it yourself then you need to reset the whole phone.
This means you lose all your images, tones and settings (Other than the standard ones)
*2767*3855# Let it go through it's shutdown and start up routine it may take a few minutes.
Note* Do not switch the phone off until it has completed its reset. Tis very bad if you do.