Losing drives and drive letters

Hi

This happened for the second time today (first time was a couple of days ago).

Today I was using the computer and downloaded around 100photos I took last night at a party. Every thing downloaded as normal I viewed them in adobe bridge (raw files), converted to jpg and posted a few on facebook. All was normal.

Then later on 2 drive drive letters were gone. No sign of any of the images or mp3s that were on that drive or another.

It's a laptop (HP) and it came with a 500gb HDD. I split into 3 with C being around 92gb, D and E being dvd rom and virtual dvd respectively.
F and G were something like 100gb and 300gb respectively.

F had around 50-60gb of mp3 and music videos, while G had a few folders of photos and a load or movies ripped from my own dvd collection.

Today when both F and G disappeared, all the mp3s, music videos, photos and ripped movies are not listed. "My Computer" is listing only C as a local disk. No F drive. No G drive.
The other night when it happened the G drive disappeared and I had to use a software recovery program to recover my files. Some were lost but since I have the dvd movies I wasn't too fussed. After I had recovered everything I made another copy on another machine.

Today it's the same again, but with 2 letters gone. Thankfully with the short time between the two I can recover most things from the other machine, but I can't recover the images I downloaded today...unless the software recovery works.

When I reassign a letter to the drive shows as empty. Interestingly, although 2 seperate drives have disappeared today, the drive space only shows up as one area so when I assign a letter to it, it's one drive - so 2 disappear and then when reassigned a letter, both have merged into one.

The machine is a few months old, maybe a year but it's not all that old.
I'm running win7 (64bit)
The partitions were created using windows originally then I downloaded Minitool Partition Home Wizard (free program and have had it installed for something like 4months - no problems.) I used MPHW a few times to adjust the size of partitions to suit my needs. Again a few months ago and no problems.

I'm ok with computers and can figure most things out but this one's got me.
Nothing has changed between downloading the images today and the drive disappearing.

Any ideas what could cause a letter to disappear??
And how to stop it happening again?
If it does, is it possible to reassign a letter without losing the info on the drive???

thanks

 

Have you tested the drive using the manufacturers diagnostics?

It may be worth checking out your hard drive using the manufacturer's disk diagnostics:

ExcelStore

Fujitsu

Hitachi/IBM

Samsung

Seagate, Maxtor, Quantum

Toshiba

Western Digital