If your cisco device has troubles booting, and you need to copy a new image to the switch/router, you can following these guide lines.
Delete the current image on the switch
Save the new image (fe c3550-i9q3l2-mz.121-22.EA7.bin).
Prepare the switch to accept the Xmodem file transfer:
copy xmodem: flash:c3550-i9q3l2-mz.121-22.EA7.bin
To send the file choose ‘Transfer > Send File’ from the top of the HyperTerminal window. Choose the ‘Xmodem’ protocol in the Send File dialog box, click ‘Browse’ in order to select the IOS image and click ‘Send’. This transfer can take up to 2 hours.
To boot the new image enter:
If no boot statement is set or if the boot statement still points to the old version, configure the correct boot statement:
switch(config)#boot system flash:c3550-i9q3l2-mz.121-22.EA7.bin