Where did my HDD size free space go?

I tried to partition my 640gb HDD. when I saw disk management I only have C drive which is 584gb recovery 14gb and OEM 100mb (i dont know what OEM is). then when i tried to shrink volume I only saw 584+++mb total size and 298+++mb only amount is available. Where did the other free space go? My laptop is new and dont have any installed software aside from the Windows 7 OS drivers & utlities abd anti-virus. thats why I wonder why i cant shrink larger volume amount.