Find the steps below for IOS upgradation of 4500 Series Cisco switches. This process is only valid when you have a standalone switch without VSS configuration.
Steps:

1. Load the new IOS image on to the Switch
   Copy the IOS image from TFTP or USB (Whatever is available)
   #copy tftp bootflash: (To copy from tftp)
   #copy usb0: bootflash: (To copy from usb. The usb number can be something else too. Check it while connecting. #show file system command can help you to verify it)
2. Verify the copied image after copy successful.
   #show bootflash: 
3. Verify the MD5 checksum for the same image.
   #verify flash:image
4. Remove the old boot command
   # no boot system flash bootflash:old-image-name
5. Set the boot variable to load with the new IOS
   # boot system flash bootflash:new-image (image is the new IOS name)
6.  Change the config-register value to 0x2102
   # config-register 0x2102 (This is essential just because in 4500 models, the default register will be 0x2101, which means load the 1st IOS image from flash. If the old IOS is in the 1st position in flash, then it will load the old one again. So, we need to change the value to 0x2102 to define that load with the image what we have set in boot variable command)
7. Save the configurations
   # write memory
8. Reload the device
   # reload
   
   

Note: The names of file system like BOOTFLASH or whatever I have used can different too. So, it’s better to verify the file system names before proceeding.