I just bought my wife a used Giant Cypress DX, 2004 or so, and wanted to upgrade the tires. I'd like a good street tire, and what she has on now is a 700x41 with a standard valve. I'd like to go presta, and a narrower tire. Maybe a 700x32 to match my own commuter bike, or maybe a slightly larger 700x35? Just wondering what the rim will handle Do I need to stick with a 700x41?

As long as the tire is not narrower than the rim then it will work OK.

You can use presta valves, but it is best to get an adapter to hold the valve stem more securely in the larger schrader hole in the rim (not the same as the pump adapter that allows you to use a schraeder pump with the presta valve, but you should get one of those, too). You can just slip the valve in and let it rattle around in the larger hole, but this can put stress on the tube near the valve and eventually cause a flat. If you can't find an adapter, in a pinch you can ask the LBS for a couple extra presta nuts and use two on each valve - one threaded right to the base of the valve stem and one threaded against the rim after the valve is put through, sandwiching the rim between the two nuts.

There are a few ways to adapt a Schrader drilled rim to Presta.

1. There are rubber grommets that go into the Schrader hole and reduce it to Presta size. They work OK but tend to pop out unless you are careful inserting the Presta valve stem.
2. There are flanged aluminum bushings that look like a tiny top hat. The are also inserted into the Schrader hole to reduce its size.
3. Less common, I've seen the little Presta nuts made with an extension collar that thread onto the presta valve stem with the collar toward the rim's hole. The collar protects the Presta stem and bushes down the rim hole.

Your LBS should have some or all of these adapters and you should use which ever you find.

Thanks! Went with a 700x38, which I think I'm pretty safe with for now. They are Michelin City Mountain Bike Tires with Protek, which seemed to get some decent reviews. I was going to buy Sunlite thorn resistent tubes, but opted against them for some reason. Any opinion on those would be appreciated. I did buy the metal flanged top hat looking Schraeder to Presta adapters, as well as the little rubber grommets. I'll use whichever I think is better at the time, but one of the reviews did say the rubber ones are more or less disposables. They tended to be destroyed after a flat. Thanks again for the help!

I had that tire on my commuter for a while and thought it did fine. At first, I felt cornering was odd due to the tread pattern but it wasn't much of an issue. I eventually went narrower and to a slick tire.

I like the City Tires and I think you will as well. I'd stick with the aluminum adapters, I'd be concerned with the rubber ones getting dislodged. No opinion on the thorn-resistant tubes, I just use regular Continentals and have been satisfied.