Since installing WIndows 7 memory has been disappearing. My C drive indicates 6.51 GB free and 139GB used. The total of the items listed in the C drive only around 22GB. I need to regain the use of the missing memory and to stop the disappearance before my computer becomes unusable.I also have a Seagate external drive. Memeory has also been disappearing. A Seagate partition is keeping a stable amount of memory.Why is this happening? What can I do to fix the problem?