If you have a wireless card, you should be able to set up an ad hoc network between your iPhone and computer. You can then use Apple's Remote to control your iTunes music.
Below are directions for doing this, which I filched from the SplashData help pages. I've included the Mac directions for the benefit of future readers. I also deleted the last step in each set of directions because they refer to connecting a SplashData product to the ad hoc network.
Creating an Ad Hoc Network
Mac OS
1. Click the Airport icon in the menu bar, and select Create Network.
2. Select options for the network such as name and if you wish to password protect it.
3. On the handheld, join the new network from the list in Settings > Wi-Fi.
Windows Vista
1. Open Connect to a Network by clicking the Start button, and then clicking Connect to
2. Click Set up a connection or network.
3. Click Set up an ad hoc (computer-to-computer) network, click Next, and then follow the steps in the wizard.
4. On the handheld, join the new network from the list in Settings > Wi-Fi.
This Vista setup information was gathered
from this documentation. Here you can find information on
setting up an Ad hoc Network in Windows XP.