1. Free up and optimize hard disk space
A hard drive that's nearly full will slow down your computer. First, get rid of temporary Internet and Windows files with the free program CCleaner.
Then, in Start>>Control Panel, run Disk Defragmenter (Optimize Drives in Windows 8) to consolidate fragmented files and folders and speed up reading and writing to the disk. Also run the Error Checking utility, which scans the drive for bad sectors and file system errors.
If you're still close to your hard drive's storage limit, consider moving your photo, video or music library to an external drive. Use a free disk-visualizing program such as WinDirStat to see what other applications and files are taking up the most space.