It is needed to clean the Junk files, temporary files, invalid registry keys (those are generated from improperly uninstalled softwares) and yes security side should be included too.
Its advisable to use Disk Cleanup utility that comes naively installed in windows 7, atleast once a week for a regular PC user. Also, dont forget to defragment your harddisk using Disk Defranmenter of Windows 7. Better the files remain uncluttered in your hard disk, its more smooth to run.
To clean junk files, if you are not sure to do it manually, you can use a freeware named CCleaner.
On the Security side, its better to use either Malwarebytes Antimalware or Microsoft Malacious Software removal tool. As you all aware of “cannot-be-overlooked” computer Viruses, spreading its wings both on the net and offline, we need some antivirus softwares. Microsoft offers Microsoft Security Essentials free of cost to Windows users or you can use FreeAvast Antivirus, or NOD32 , Norton AntiVirus as paid options.
It is always look nice when a clean Windows PC in front of any level of user. Cobwebs on ventilation fans, dirts on keyboard, dust on monitor not only look horrible, but also its bad for your PC’s health too.
“Your computer could fry if you don’t keep it clean,” says Jonathon Millman, chief technology officer for Hooplah Interactive.