Contact reply format and jumbled text

I have a client who has my first test of a contact response form and I ran into 2 problems. 1. The captcha was unreadable. i couldn't read it myself, so I dropped that.
2. She says on Windows Outlook Vista, when she hits reply, the background is black and the text is black, even though it comes in as html with black text on white. When I hit reply on the Mac, Entourage, it is in the same form as it came in, black on white.
3. When someone replied to her corrected reply (she set text to white on black I think), the reply from her customer came back as jumbled or garbage text, like UTF something perhaps.

Wondering what the solution or fix might be.