Partition disappears

I have a problem with my computer and I hope that you can help me:
Out of the blue, my E partition have suddenly started disappearing.
I can find it under diskmanagement where it has been transformed into an OEM partition and i have also managed to turn it back into a normal partition with the diskpart tool.
But everytime I restart, it is OEM again.

Somewhere else, I have read, that the problem could be Acer Arcade. I removed it from my machine but the problem persists.
And it is really bugging me - any suggestions for this behaviour?

Hi WHS
I have tried assigning a G to the partition instead, but with the same result.
Yes, I have an Acer Aspire 8920G.
I will try to disable the Acer processes tomorrow.
Right now, I am trying out this solution that I found on techguy:
Solved: Hard Drive Partition has Disappeared, - Tech Support Guy Forums

Clean reinstalling without the Acer bloatware will give you a much more repsonsive Win7.

Did you by chance get the Acer Upgrade Kit which includes a clean-copy Win7 install DVD? Or do you have access to one?

Hi WHS and gregrocker
Thank you for your interest.
I'm afraid I really screwed things up, when i used the testdisk program described in the link.
Now, my computer can't boot, and when I boot up from my windows disk and go into repair and then diskpart - it shows the former primary partition, my boot partition, as 0 bytes and I cannot select it...
Hmmm...
Don't do stuff like this in the night.
Well, tomorrow morning I am leaving for a vacation. We are going to the Alps and I am planning on forgetting all about my computer in that time and then come back to the machine, and to my post here by start June.
Greetings from doublejoble
Denmark

You may not need to reinstall if it is only the 100mb System Reserved boot partition which was deleted.

If you still have the WIn7 partition intact, then mark it active using free Partition Wizard bootable CD which will also allow you to Explore your files to make sure they are intact, and resize Win7 to include the lost partition.

Then once WIn7 partition is marked Active, boot into the Win7 DVD Repair console or Repair CD, click through to Recovery Tools list to run Startup Repair up to 3 separate times with reboots to write the System MBR to Win7 partition.

Hello again
Now I am back from my holiday - we ended up in Schwarzwald in southern Germany and had a wonderful time there.
I managed to make my computer bootable again with the testdisk program by making c: the boot-drive again.
And then I also managed to make my e: drive stay visible by booting up from my Window 7 bootdvd, entering the repair mode, opening a command prompt and using the bootrec.exe /fixmbr command.
What a victory.
Now I thinking about whether I dare trying installing the Acer Arcade deluxe program again, which somewhere is listed as the root of this evil.
Greetings from Doublejoble
Denmark

Set a restore point first before you reinstall it.

You might want to also save externally a Win7 Backup Image if your Win7 is running as you like it.