text: will frequent defragmentation slow down or damge your computer? what happens to my computer if i perform defragmentation once in every week? defragmenting an hard disk will improve the performance . it actually rearranges the data clusters is a sequential form so that the parts of files which are located in different areas of hardisk are brought together. so there no impact on harddrive nor computer..  but i suggest u to run defrag aleast 15-25 days interval.