Photoshop help

With all your wonderful help, I have finally fixed the problem. Thank you so much for your time and effort into helping me solve these problems - can anyone help me save these to memories - mods maybe - so they can help others in the future? *hugs everyone*

I have looked on memories and FAQ and I couldn't find an answer there. If the answer is there, could someone please point me in the right direction?

I use PS7 and have been for several years. Recently something changed on PS and I have no idea what I did to change it and in the progress of trying to change it back, something else has gone wrong. See... I should have asked first *rolls eyes*
EDIT The answer to the black background is hold the shift key down and paint the background with the paint bucket with the colour of your choice. Thank you everyone for your help.

Okay... The first thing that went wrong is you know the background that is immediately behind the picture you're working on? Well it has gone black. Before it was a mid grey - there is a small piccie here showing the black frame around the photo - if you want to see it better there is a larger one linked. large one here

second, you will see the grid lines all over the picture - I know how to temporarily get rid of the lines, but have no idea how to get rid of them permanently when I open up a new picture - getting rather irritating *and yes, this was one of my extras I accumilated when I was trying to fix the black background*

I am also getting this pop up when I open PS You currently have Adobe Photoshop's primary Scratch and Windows' primary paging file on the same volume, which can result in reduced performance. It is recommended that you set Adobe Photoshop's primary Scratch volume to be on a different volume, preferably on a different physical drive.

As you can see, I have quite a few problems. To try and sort it out, I have completely reinstalled PS twice and rebooted.

If anyone can help me I would be really thankful. The black background is the most irritating as I can't work with black on the icon or art as it disappears and I have no idea where my work is lol.