Cisco catalyst 4948, 4900 switch factory reset

Step 1:
Click here to learn serial connection using console cable

Step 2:
 Use following parameters in putty and click Open

Step 3: Turn on the switch Press "ctrl + c" to go into the rommon mode

Step 4: Write "confreg" in rommon mode

do you wish to change the configuration? y/n: hit Y
enable "diagnostic mode"? y/n:  Press enter
enable "use net in IP bcast address"? y/n: Press enter
disable "load rom after netboot fails"? y/n: Press enter
enable "use all zero broadcast"? y/n: Press enter
enable "break/abort has effect"? y/n: Press enter
enable "ignore system config info"? y/n : hit Y   (Only in this option select yes) 
change console baud rate? y/n: Press enter
change the boot characteristics? y/n [n]:Press enter

Step 5: Write "reset" to reboot and save changes

Step 6: It will ask you after booting: inital config dialog - Press "No"

Step 7:  Write "enable" command

Step 8: Write "Write erase" command to erase startup configuration of the router and reset it to factory default. Remove passwords if any...

Step 9: Use "sh hardware" or "sh ver" commands to get detail about processor & image of the router...  

Step 10: Use "sh env all" to display all environmental monitor parameters i.e. Power supplies, fan speed, temperature readings, etc..

Click here to see full reset guide