Nobody can tell you anything. You are not providing any system information or otehr details that may be relevant.
Processor: AMD Athlon II X4 640
Ram: 8 GB
Windows 7 64 bit
2 TB Harddisk
I have the same issue on a windows 7 Intel core i3 Asus laptop.... Except mine stops at 56%
I really hope someone has the answer... I need photoshop for this semester at university!