I haven't seen a window like that in ages. Have a look at the site:

http://www.do-it-yourself-help.com/window_sash_cord_repair.html


Good link. If you live in a northern climate, it's too much effort
reworking an existing window like that. If you're on a budget (and
even if you're not...), Menard's has on-the-shelf pocket (replacement)
single-hung windows for $99 after rebate, and in today's flier they
have Jeld-Wen double-hungs for $130 or so. Any of them would be about
a hundred times more efficient & comfortable than what you have now.

It looks like you're on the second floor, so a minimum of ladder work
would be called for, but when you're done you're DONE. You can fill
those counterweight cavities with expanding foam and stay cozy & warm
all winter.