Answer by Indrek for Why does the cd command occasionally take several seconds to complete?

A couple of things to try:

1. Defragment the hard drive. The built-in defrag utility is fine, though for more advanced tuning (system file defragmentation, free space consolidation etc.) you can look into third-party programs like Auslogics Disk Defrag.
2. Check the hard drive's SMART attributes with HD Tune or similar program. See the Wikipedia article for a list of attributes, including those that are potential indicators of hardware problems.
3. Run chkdsk to find and fix errors with the filesystem and bad sectors on the hard drive.