Ever since I downloaded ImproveSpeedPC my Flash Player keeps crashing and I can't download anything.
Applications like these do more harm then good when it's about cleaning entries in the registry or deleting unused file. I believe that the application deleted important files and registry keys that were not meant to be deleted.
Please install Combofix and perform a scan of your computer then install Adobe Flash Player again. You might need to install the version for Internet Explorer and the version for Other Browsers.