I have a new 2003 Accord Coupe EX-V6. When I roll the passenger side window down all the way, it squeeks when coming back up. It's a pretty annoying sound. I was told that I can apply some silicone lubricant to make it go away. My question is, has anyone ever applied this stuff and what exactly is this lubricant and where can I buy some.

Do you know if the noise is coming from the glass sliding on the guides or from the window actuator?

It's from the glass sliding on the guides. I think I'm pretty sure of that. One thing to add is that it didn't start squeeking until after I got the windows tinted. On that note, if I have to "lubricate" the windows in any way, will it hurt the tinting?

That explains a lot. The squeaking probably has to do with the small bit of added thickness added to the window. A guess would be the "belt moulding", or part along the bottom of the window at the top of the door. Try holding that away from the window and see if that cures it. At least at that point, you'll know what to lubricate.