You may be best served by posting a HijackThis log, but if you're hesitant to do it, and if per chance it's something other than the ISM, you can try downloading and installing (free) Malwarebytes' Anti-Malware. It may (or may not) find something.
You can download it from here:
http://www.majorgeeks.com/Malwarebytes_Anti-Malware_d5756.html
Save it to your Desktop, or somewhere you know you'll find it, in order to install it. Double Click mbam-setup.exe to install the application.
* Make sure a checkmark is placed next to Update Malwarebytes' Anti-Malware and Launch Malwarebytes' Anti-Malware, then click Finish.
* If an update is found, it will download and install the latest version.
* Once the program has loaded, select "Perform Quick Scan", then click Scan.
* The scan may take some time to finish,so please be patient.
* When the scan is complete, click OK, then Show Results to view the results.
* Make sure that everything is checked, and click Remove Selected.
* When disinfection is completed, a log will open in Notepad and you may be prompted to Restart.
* The log is automatically saved by MBAM and can be viewed by clicking the Logs tab in MBAM.
Extra Note:
If MBAM encounters a file that is difficult to remove,you will be presented with 1 of 2 prompts,click OK to either and let MBAM proceed with the disinfection process,if asked to restart the computer,please do so immediately.
**If you encounter this message:"c:\program files\malwarebytes' Anti-Malware\mbamext.dll Unable to register the dll/ocx: RegSvr32 failed with exit code 0x5" Click on ignore mbamext.dll