please check to see if your hard disk is fragmented and do a defragmentation if necessary. Please click on the my computer icon and go to the drives you have on the HDD one at a time. Right click on the drive and click on properties. Go to the tools tab and click defragment now. Analyze defragmentation and if you're told that you need to defragment the drive do it.
maybe something nasty slowing it down ,start with this after you do othere suggestions .
Download Malwarebytes' Anti-Malware (http://www.malwarebytes.org/) to your desktop.
* Double-click mbam-setup.exe and follow the prompts to install the program.
* At the end, be sure to checkmark the 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 full scan, then click Scan.
* When the scan is complete, click OK, then Show Results to view the results.
* Be sure that everything is checked, and click Remove Selected.
* When completed, a log will open in Notepad.
post the log back here