I have used both Time Capsule and a Netgear router - both are very good. If you use Apple products, they are generally much easier to set up I have found.
If your macbook is newer, it will probably support 802.11n which is faster than 802.11x (where x is any other letter) - so to ensure you are allowing your macbook is reaching it's potential, you may want to get a 802.11n compatible router (all Apple products are 802.11n compatible).
If your PC does not already have a wireless card, you can either hook it up to your router via ethernet (not available on the Airport Express however, as that only has one ethernet port which you'll need to connect it to your modem) or buy a wireless card (they're fairly cheap). If you opt for a wireless card and have also opted for a 802.11n compatible router, you'll want to get an 802.11n card, again so it is as fast as it can be.
Also worth noting is that some routers are routers and modems in one. Apple products are not. I'm assuming you already have a modem but could you run the model number by us? Some modems that ISPs provide connect via USB as opposed to ethernet, which is not what you want.
Also worth noting if your Macbook has Leopard is Time Capsule - if you haven't already looked into it, it might be worth researching.