Actually, lionel77, aMule doesn't allocate the full space required for a file on receipt of the first byte. Rather, each byte it receives is just put in the proper place in the file. So, if a byte belongs at the beginning of the file, the file system will only allocate the first block. If it belongs in the middle of the file, the file system will allocate enough space to cover from the beginning to the middle. If it belongs at the end, the file system will make sure the full size of the file is allocated.
So, it is not true that if a file has more than 0.0% download progress all of the necessary space has already been allocated. The only sure fire way to make sure you don't run out of space is never start downloads the sum total of whose sizes is more than your free space.
So, the fix for underhosi's problem may be more complicated than you suggest. It's currently hard to tell how much space has actually been allocated for a given partial download and how much it will need to complete. You have to determine its part file number, go to the Temp directory, and check the size of the .part file. Then subtract that from the total size that it will be when completed (as reported by aMule). The result is the amount of free space you will need for it to successfully complete.
Using that method, find a download which has been completely allocated, or which has enough space to completely download. Resume that download. Let it complete. When you're done with it, remove it from your hard drive to free up some room. Now repeat the process with the next download.
Or, of course, you could just free up enough room on your drive to accomodate all of the downloads you started and resume them all. Or, cancel some downloads for whom space has been allocated, but which you don't need urgently. You can always download them later. Then resume the rest.
The bottom line is that aMule can't manufacture new hard drive space. You have to have enough available for the things you're trying to download. What exactly did you expect to happen when you started more downloads than you could fit on your disk?