nnbnbhi,
the best way to test your bandwidth is to use something which your ISP prescribes to check your bandwidth. any other website would be testing data transfer rates between your computers and their servers. hence you will not get the entire picture.
if your agreed bandwidth is 256 kbps, and your are only getting 16 kbps, there is a huge short fall.
i would suggest your check your CPE device or devices and all other network nodes. the best way to do this is to study the packets travelling between machines.
try ethereal
www.ethereal.com/
it will help you study the packets flying about in your network. you might be able to pin point to the rougue device in your network, or even challenge your ISP for low quality of service.
