HDD worked at 1st,then disappeared

I bought a new pc a year and 1/2 ago it’s specs are - Asus P6T SE motherboard - Intel corei7 920@2.67GHz - 6GB Corsair dominator DDR3 - nVidia GTX260 - Corsair TX750w power supply -1TB Western Digital green WD10EADS 00L5B1 - Windows 7 home 64bit - LG dvd drive - and a Asus blu ray drive i added about 6 months ago.My hard drive is about 90% full so i ordered a Western Digital 2TB WD20EARS.The 1TB HDD is connected to SATA 1,the LG drive to SATA 2,the Asus drive to SATA 5,and 3 & 4 are behind the graphics card,so i put the new HDD on SATA 6.I booted Windows as normal,it recognized it and installed the drivers,i went to disk management,it popped up asking me to initialize the new HDD,i did so in MBR style.I clicked on the drive in disk management,right clicked and went to ‘New Simple Volume’,partitioned it as 1 space,gave it letter F,did a quick format with File System:NTFS/Allocation Size:Default.It appeared to had gone successful.I was able to find it on the pc and copied 16.8GB of music and video on to it in like 3-5 mins.I was able to access all the files afterwards and played a few files,everything opened and played fine.I went to transfer some more files,like 20GB or so and it took like 30-45 mins to transfer.Now when i went to play files in either folder on the new drive it took about 60 secs or longer to open or play a file and escalated to where it wouldn’t open anything on the new drive,it just kept spinning on the windows progress symbol.The same files on tho old drive played fine.So i restarted the pc,and the same happened.Files played fine for like 5-10 mins,then slowed down and progressed to not playing at all.I turned it off,unplugged the pc and switched the HDD’s SATA port 6 with the Asus drive on port 5.When i booted it up it recognized both the HDD and the blu ray drive and installed drivers.I deleted the data on the HDD and copied the same 16.8GB of data to the drive just for time comparison and it took the same 3-5 mins to copy.Files played quick as normal.So i tried to copy another 13GB of data to it and it started going slow again,got to about 75% complete and the progress bar window disappeared,and when i went to look for the drive on my pc it was gone as well.I tried different SATA cables,and different ports.I even got to ports 3 & 4 and tried them,and when i tried port 3 my pc wouldn’t boot windows,just said some error message.I moved it back to 6,and it boots fine just still won’t recognize the new drive,it dosen’t show up in my pc,BIOS,or Data Lifeguard Diagnostics.I also changed my power setting to high performance for hard drives and disabled sleep and all that.This is the 1st hard drive i’ve ever installed myself,do i have a bad drive???

Test the drive with Data Lifeguard Diagnosticsand it should try to repair the drive if any errors are encountered, if it fails the extended test or the errors can not be repaired, the drive might need to be replaced.