Hey Gang,
I've just discovered on my 5 yr old double hung windows that the vertical tracks they slide on are sort of pushed back and slack.  They are almost like they should be filled with something and aren't.  They are semi rigid plastic and I was thinking of drilling a small hole and squirting in just enough foam to get them to seat properly to the space in the window they were made to fit into.  Am I explaining this ok?  I can see a little bit o' light and obviously feel the infiltration that these slack seals cause.  Suggestions?  Replacing them is not an option $$$$.  Thanks for any advice.
Scott

Contact the window manufacture to ask them how to fix it. If you don't know who made them, there may be a label in the corner of the glass that tells. Five year old windows may still be under warranty. No need to DIY it if they'll do it for you.

Thanks for the reply.  I'll give it a shot.

Are they pushed back and slack the entire height of the window or just near the center of the frame?
If it's just near the center the windows were most likely installed improperly, the frames weren't straightended upon install. You can test this by slightly raising the bottom sash and trying to "rock" the sash, you shouldn't be able too. If they are slack the whole way the plastic either broke or your frame rotted out or they are really really cheap windows.
There is usually nothing between the plastic guide and the window frame except for a piece of foam for half assed insulation. Drilling a hole and inserting expanding foam would potentially prevent you from getting the sashes out should you need too, as you need flexibility in the guide to release the top of the sash. That is the problem with that dbl hung design.

On the ones that are slack, it is more at the bottom of the window track and they have about 1/4" play. The ones that are "tight" have close to zero play. I didn't see a manufacturer etched or stamped anywhere, but it is night time. It was new construction and the builders around here put a higher premium on gittin' er done than anything else, so I would think it was a poor install. I can rock the sash about 1/8" on the loose ones and almost none on the others. Thanks for the replies, I'll try to track down the manufacturer or sub info. and go from there.