PremiumSearch is malicious adware.  It may add a toolbar that might look like a Google toolbar but will change your Internet Explorer homepage.  It will also redirect your search requests through PremiumSearch search engine without your consent. You will also be bombarded with annoying pop-up ads.  This is in an effort to direct you to sites that contain pirated software and pornography.
If your computer is infected with this harmful parasite, it is imperative that you remove it as soon as possible.  It will do nothing but harm to your computer and will degrade its performance considerably.  In order to fix this problem, you should try and trusted anti-spyware program such as SpyZooka to get rid of this problem.