Leaking around bottom corner of window?

I bought my 100 yr. old house about a year ago. I started removing wallpaper in my living room last night and it looks like at one point there was some water leakage in the lower right hand corner of the window. There is also a black powdery area that I am assuming is mold. It doesn't look like the leakage was recent. I am going to take care of the mold with a bleach/water solution.

At some point in the last 30 years, aluminum storm windows were put on the original double hung windows and aluminum was fitted around the outside trim. Can I assume this solved the leakage problem or do I need to have it examined more closely? If there is still a problem what can I do about it?

Thanks for your help!


p.s. Humidity in the house doesn't seem to be a problem and I don't plan on re-wallpapering.

 

The mold could be due to either a leak, or due to condensation. It could have occured at pretty much anytime during the past 100 years. It may or may not be a problem now.

If it were my house, the wood double hungs would be gone, there would be vinyls in there place, and the 30% to 50% savings on my heating and cooling costs would be paying for the change-out.

 

New windows would be nice, but they are not in the budget right now. I have to get the roof repaired first. =(