Where does all the 'improvement' in CPU and memory go to? Blame your antivirus.
The worst offenders are the anti-virus suites with real-time protection. According to these results, the latest Norton Internet Security degrades boot
time by nearly 50 percent. And no, that isn't a typo in the disk column.
It also makes all disk access sixteen times slower! Even the better performers in this table would have a profoundly negative impact on your PC's
performance. Windows Defender, for example, "only" makes hard drive access 54 percent slower.
More interesting information (but alas little help) here.