Are you reimaging the machine the image was created on, or an identical model?
Which operating system are you re-imaging?
USB support is native to XP and later operating systems, so unless the DELL machine has a chipset that is not natively recognised and supported by XP, there should be no issues with USB.
The test is to clean the hard disk of any existing operating systems and install your operating system manually without any additional drivers, then check if USB support is present or not.
If it isn't, then you need to find the correct driver, then check if the driver is in your image, and also in the plug and play search path within sysprep. (I'm assuming you are sysprepping your images).