Duplicate emails deletion

[#1]

Help, I have found 37,400 emails in my inbox because there are 30-40 duplicates of the same message! sadly i don't have that many friends so most of the messages need deleting!
I have tried the manual method of going through and deleting the multiple copies of the same message but it is taking me forever, selecting them all and then scrolling through unmarking one of each message and deleting the rest!
Does anyone have a suggestion of how I can delete the duplicates quicker and easier before it sends me completely crazy!! I want to back up all my 'bits and pieces' but without so many emails!
As always your kind advice very much appreciated, I am really cautious of the 'programs' I see all over the internet saying they will do what I need but how do I know which to trust!
System, Windows 7, email program, Windows Live mail.

[#2]

I've been pondering a sensible way to approach this, and just had this thought, so hope it helps.
Create a new folder called "Sort" or whatever you like. Select All and move them to the new folder.
Go through the new folder and select one copy of each of the ones that you want and move them back to your Inbox.
You are then left with all the ones you don't want in the new folder, so you can use "Select All" and then delete the lot.
I did initially think of doing this the other way around but decided the above was safer as you may not spot a new mail coming into the Inbox in the meantime and might have deleted it accidentally..