Verify the Cisco upgrade path.
Download the latest IOS image for your cisco website
Go to cisco.com -> IOS Software -> Select your Siwtch (for example: Cisco Catalyst Switch 3750G-24T) -> Click on “Download IP BASE” -> Select the latest version that you want to download (for example: 12-2.55.SE1).
While you are on this download page, copy/paste the MD5 given to your system. After we download the IOS image and move it to the switch, we’ll verify the MD5 checksum before installing the image.
Copy the image file from your laptop to the switch using TFTP Server.
# copy tftp flash:
Verify and load the boot.
#boot system switch all flash:c3750-ipbasek9-mz-122-55.SE1.bin
Save and reboot