I doubt that it's RAM! In answer to the original question you can have as many partitions as you might reasonably want (but if you want more than 4 on one hard disk then you'll have to make one of them an extended partition within which you create logical drives).
What do you mean "shows unallocated in Windows 7. I can't use that space"? Shows where? Are you saying that in Disk Management it shows as unallocated space but it won't allow you to create a partition using it? How many partitions do you already have?