Furniture, Wood and Cabinetry Finishing - Sanding wooden windows

My house has wooden windows and the bathroom window has some mold on the window. This was due to a bathroom fan that needed to be replaced. With the fan fixed, the moisture is gone. Now I want to sand and re-stain the window. At least that was my plan. The sand paper is doing something, but not taking all the black spots off. Is this the best way to approach this? I could certainly get rougher paper and put in more elbow grease, but is this the best thing to do. Are there any products to use? After a search here on the subject some say bleach, some say that will discolor. Not sure how to continue.

Any advice would be appreciated. Thanks in advance.

A bleach/water solution is almost always the 1st choice. If the wood is sealed with varnish/poly, the bleach won't affect the wood.

That brings up a good point I didn't mention. I believe the wood is untreated.

It would be odd for a window to not have any finish applied but.........:eek:

I think I would still use a bleach solution - not stronger than 50/50, rinse well. Sand when dry, dust and maybe wipe down with a thinner rag. While the wood is wet with thinner, that will give you an idea of how well it will stain although no bigger than the wooden sash is, I doubt color differences in the stain will be overly noticable.

I know it would be odd for the window not to have any finish, and I'm no expert, the window sill and the wood trim around the window definitely have a smoother or different "finish" than the wood of the actual window. The would of the window just feels more bare. When I bought the house the previous owners just finished the upstairs and I always thought someone just ran out of time or got lazy. All the upstairs windows are this way.

Thanks marksr...you confirmed what I need to do. I'm going to try it out!