Opening new file in Photoshop

I'm having the weirdest problem. I don't know that I've ever had to deal with it before. I was working in Photoshop 7, and made a lot of mood theme icons. I was continuing working in Photoshop, when all of a sudden, when I did File - New, it opened a 15 x 10 grayscale file. When you work in Photoshop and you save something, it SHOULD have the settings (size and RGB mode) that are the same as the previously opened file when you open a new one, right? But it's not doing that. I closed and restarted the program, but it's STILL doing it. Every time I try to open a new file, it's not giving me the size that I've been using. It keeps opening 15 x 10 grayscale files. The weird thing is that I don't think I changed anything, but it just started and kept doing it while it was working fine earlier.

Can someone please help me? I'd really appreciate a fix! Thank you.