The importance of vector instructions is growing in modern computers. Almost all architectures include some form of vector instructions and the tendency is for the size of the instructions to grow with newer designs. To take advantage of the performance that these systems offer, it is imperative that programs use these instructions, and yet they do not always do so. The tools to take advantage of these extensions require programmer assistance either by hand coding or providing hints to the compiler. We present Vector Seeker, a tool to help investigate vector parallelism in existing codes. Vector Seeker runs with the execution of a program to optimistically measure the vector parallelism that is present. Besides describing Vector Seeker, the paper also evaluates its effectiveness using two applications from Petascale Application Collaboration Teams (PACT) and eight applications from Media Bench II. These results are compared to known results from manual vectorization studies. Finally, we use the tool to automatically analyze codes from Numerical Recipes and TSVC and then compare the results with the automatic vectorization algorithms of Intel's ICC.