This is the trickiest of the installation for 5.00 M33. Ok, make sure you are not connected using the USB connection menu. Exit that menu if you are. I have to presumed you had flashed 5.00 M33, because this file is patched on top of that firmware. What you need to do now is :
1. Press and hold [Select]
2. Change the USB Device to Flash 0
Now activate the USB connection menu. Go to this new weird drive. If you cannot see "KB" folder, make sure you unhide system and hidden directory in your Windows. Now, extract the package you download here to the root of this drive. Safe remove the drive and exit USB menu.
Repeat the above steps, but set it back to Memory Stick. You have just flashed a file into the firmware and this patch is done.
Download the PSX fix for 5.00 M33:
PSP 5.00 M33 PSX Fix
Basically, just for the fun of it. I heard that Popsloader still does not work properly and PSx seems to be a big problem in 5.x firmware. So, if you are a hardcode PSX gamer on PSP, I would suggest skipping the whole 5.00 M33 until I say its good for PSX. :)
Lastly, why this is v2, apparently, v1 doesn't work so well.