Depending on the processor and GPU 3 years might not make it time for replacement. Comparing its processor benchmark scores to newer ones in your price range can give some idea if a upgrade is worth it. There are a lot of slow processors out there in lower and medium priced computers these days with the push to lower TDP wattage usage. The problem you described sounded much more like a Malware or other malicious software hijack/redirect problem to me.
Make sure your operating system, browser, browser plug ins, are up to date. Then scan it with at least two reliable and up to date anti virus/malware programs.