Firmware 4SDM1 or 5SDM1 to fix clicking noise on Seagate hard drive?

I am using a Seagate hard drive which makes a strange clicking sound when in use. I searched on internet to find the possible reason for this sound and found that this problem exists in many other hard disks manufactured by Seagate. Also I found that Seagate has released a new patch for the hard disks to solve the problem of the clicking noise. The hard drive that I use has firmware 2SDM1. Now on the website of Seagate, I found that there are two firmwares, Firmware 4SDM1 and Firmware 5SDM1. Now I am confused which firmware I should I upgrade my hard disk with? If anything goes wrong, it might render my hard drive useless for long time. So can anyone tell me which firmware should I install to upgrade my hard drive?

I too downloaded the firmwares and I too got confused among them as they both were very identical in functioning and working. I downloaded both the files and opened them using Winzip. Before the extraction of inner content, I compared their size and CRC. To my surprise, both of them very extremely identical for each and every file in the package. There was not even a minute difference that would help to distinguish between them. I tried various versions of this firmware; from downloadable .zip file to .iso files. But all the versions had same files in both the firmwares. Even though they seem so similar, many people are facing problem with firmware not being accepted by the hard drive when wrong version is installed.

The Seagate ST9320423AS firmware is compatible with following hard drives,

• 160G - ST9160412AS DP/N J423T
• 150G - ST9250410AS DP/N K556T
• 320G - ST9320423AS DP/N F729T
• 500G - ST9500420AS DP/N G629T

If you are trying to update your firmware using this update patch, then it is recommended that it should be installed during an regular update cycle. This firmware, once installed will make itself compatible with other firmwares, drivers, hardware and BIOS of your computer. This firmware will update the hard drive and will also stop the clicking noise that is heard from the hard drive. See to it that you are supplying AC power to the hard drive without any interruption.

I have downloaded Seagate ST9500420ASG and it worked great with my 250G - ST9250410ASG DP/N C385R. The other hard disks with whom it is compatible are 80G - ST980412ASG DP/N FC63Y, 160G - ST9160412ASG DP/N C384R, 320G - ST9320423ASG DP/N C386R and 500G - ST9500420ASG DP/N D111N. It will stop the clicking noise once the hard disk is updated using this firmware. I think that this firmwares will work best when installed by making the bootable CD of it. Installing it during the run time may not provide it enough control over the hardware as many processes will be simultaneously accessing the data in the hard drive. But when done using bootable disk, very less number of processes will be working on the hard drive that has to be updated.