I am trying to deal with my problem for hours but i have no more ideas what I can do. I want to transfer the mp3 files and jpg files from my PC to BB(8800). I have installed Desktop Manager but I still can't transfer it. I also went to L: (which is a new device that my pc has found which is a BB, but I can't get into it either) It says: Insert disk to L:. Please, help me!

Portable

Welcome to the BBForums.

It is actually easier than this, and you don't need Desktop Manager.

See the link here with instructions to enable Mass Storage on the Card.
How do I add media files to my microSD card? - BlackBerryFAQ

Well, I did everything as it says on the website you gave me, but, as in first option: 3. A pop up box will open, select Open folder to view files using Windows Explorer this window does not pop up, and as in second option: 2. Select Media Manager I do not have anything like media manager shown on my desktop manager.

I think I know what might be the problem here. On my BB it says that my me microsd card is not formatted, (I have got this one from my other phone nokia n95), so, can you tell me how can I format it?

Portable

I got into options and Im trying to format it, but it says: Media Card Format failed. Do you think it might because it is from Nokia n95?

Portable

Options > Media Card > Menu > Format.

Could be. Try formatting it on your PC with it in a card reader.

you are confusing/mixing instructions from two different options.

Decide first if you want to use Media Manager or not, or Mass Storage Mode.