Display Problems - PLEASE HELP !!!

  I have windows Xp
And im using a 42 inch Hdtv as my monitor.

I Set up my media center but im having one of 2 problems.

1. By accident i dont know what i did, while adjusting the resolution media
center adjusted and now the Top bar and the bottom Play controls are not
attached to the top and bottom edges its in the middle of the screen. It was
perfect in the beginning i dont know what i did

Is there away to restore default and just over again (Not Go through the
wizard again iv done that already)

2.Also when i watch tv , The picture is does not fit my screen.
Its just just squeezed in the middle , when there is plenty of space to be
used.
Iv gone through the wizard guide over a dozen times. Nothing changes

Please help -  This is really on nerves

Thanks