no problem!
Really, any program can be used. Some of the more popular ones are photoshop, manga studio, and paint tool SAI. People also use paint.net, ms paint, gimp, and a variety of other programs, combinations of, or you can even make pages the good ol traditional way and scan them in!
for me personally, I use a combination of photoshop CS2 (which is available free on the Adobe site, as they have stopped creating updates/support for it, but it works pretty great for me!) and paint tool SAI (Which I did purchase a license for, as it was only about $70)
PS I use for the panelling, for text and bubbles, and other small additional effects. I use SAI for sketching, line art, and most of the colouring/painting process as I like the way it functions and the tools better (if only it had a text tool, I might switch over to it entirely ;_;)
But there are TONS of programs out there that are readily available to you for the general art process for making any sort of comic.