Erasing tool not working...

Hello

Ok, i've been playing around with photoshop for a few weeks now and i'm making some signatures for the reptile sites i use out of photos taken.

I have one photo of a lizard that is on a white flooring, so i was trying to replace the white with a brown colour using the colour replacement tool. It went horribly... I kept playing with the options but the white just got replaced by pale, obvious colours no matter which colours i picked so i gave up.

Now i was getting into another pic and want to erase the background and after selecting the eraser tool, it just started colouring it in with the fore-colour instead of erasing. I've tried changing the colour replacement options and got it so that it just does nothing when i try to erase.

My colour replacement settings are:
mode - hue
sampling - continuous
limits - contiguous
tolerence - 30%
anti-alias ticked

My eraser settings are:
brush
opacity - 100%
flow - 100%
erase to history ticked.

Can anyone help me please? :(

Even if you can just tell me how i can reset my photoshop back to default settings that would be great...

Thanks

Please? I'd really appreciate it... :confused:

Make sure you are not using the masking function

To set photoshop defaults on PC - do the following :

First, hold down all three Ctrl+Alt+Shift buttons
Now while keeping those button held, simply open Photoshop or a file that opens with Photoshop
As Photoshop loads, you should get a prompt asking if you would like to "delete the Photoshop settings file", Click yes
You should now have a fresh slate with all of the settings returned to their default.