Acer c: & Acer data d: d was showing now its gone!! hel

[auto7890]

I finally removed my hdd out my acer notebook and put it into an external
enclosure and connected it to my desktop pc.

It found C: on that drive which it replaced with an F:, but D: on that drive was no where to be found until I went into Computer management and manually typed in D: for that partition. I then saw and red all my files on that.
The real problem wasn't until I switched on my pc the next day and this
D: was gone again.
I then went back into computer management and tried to type in D: for that
partition but this time it came up with an error saying "can not apply drive letter until you enable volume read, reboot to enable volume read",
well I rebooted the computer ,but no D: was anywhere to be seen.
Please help, what do I need to do to get this back ?

[NickS]

I think you need to go back into Disk Management and see what physical drives and partitions are shown there. If the external drive first partition (old "C:") came up as "F:", there were probably other assignments already for D: and E: (maybe for CD, removable drive, etc). It would have been logical to assign the external drive second partition "G:"