If it’s 359.3, you have old bootrom. If it’s 359.3.2 or anything above that, its a new bootrom.
on Windows 7/Vista/XP
Step 1: Put your iPhone into DFU Mode (not recovery mode)
Connect your iPhone to your computer.
Turn iPhone off.
Start iTunes.
Hold Power and Home buttons together for 10 seconds or so.
Release Power button but keep holding the Home button until your computer recognizes a new USB device.
iTunes will now recognize your iPhone.
Note: Your iPhone screen at this time should be blank (black in color), if not, then you are most likely in Recovery Mode, not DFU mode.
Step 2: Right Click on My Computer and click on: Properties -> Hardware (tab) -> Device Manager
Step 3: Select the “+” to open submenus tree items for "Universal Serial Bus (USB) Controller".
Step 4: Now look for "Apple Mobile Device USB Driver", right click and select Properties.
Step 5: Go to "Details" and find "Device Instance ID".
Step 6: Simply scroll through the string and you’ll find the bootrom version (iBoot) as shown in the screenshots below:
