Version V4 is the same as V3 with the only difference being that there is a NEW backdoor script which has some additional features to protect root(#) from getting broken when you do an OTA. I also applied these to this flash image so you wouldn't have to add the additional protection yourself. V4 also has the drivers for XP included. However, when taking an OTA you should also install the backdoor for additional protection. However, you cannot leave the backdoor installed as it turns off sound. So having a little more protection just might save your root in case you take an OTA and forget to install the backdoor.
Alternative download location:
Not sure if v3 is still available - v4 is though.
ReadMe is in the zip folder, suggest you read thru it first before u do anything