You can choose to transfer files between PC and Samsung Illusion via USB cable. Here are step by step guides for you:
Step 1. Configure the USB Settings
From the Home screen, press the Menu Key, then touch Settings ➔ USB Settings ➔USB mode ➔ Mass storage mode.
Step 2. Attach your phone to the computer with a USB cable. Your Samsung Illusion phone will recognize the USB connection and displays the USB icon and the USB mass storage screen.
Step 3. On the USB mass storage screen, touch Connect storage to PC to enable copying of files between your computer and
the memory card.
Step 4. At the prompt on the computer, select a transfer method.
Step 5. Transfer files to the memory card. When finished, you can disconnect the USB cable.
For your information, the Samsung Illusion supports two USB connection mode: one is the Mass storage mode,which is used for transferring files. Another is Internet connection mode, which enable other device to use your Samsung Illusion connection. if you want to use your phone as modem, or tethering. go settings-usb settings- usb mode, internet connection mode.