Thanks, Adam.
I have fixed the problem by increasing the entry of "Maximum Requesting Entity Body Limit" from 200000 to 20000000 from IIS 7 ASP option.
Anyway, i got second problem on the uploading size, how can i change the upload size as default 1000K (1MB) to 10000k (10MB)? Because some of our product catalogue pdf file which is larged then 5000K (5MB and above). please help~!