Several things... Chech your registy for the key in HKey_local_machine\software\microsoft\windows\curr entverion\run
see if that is there or if there are suspicious paths there. Also, check your running services, as it's possible you have A. a virus, B. another form of malware that has gotten installed and is doing this to you.
CWShreader might be good to run as well as adaware se and any virus program you have. See what shows up...