Given below are freeware programs that you can download and use for free.

Using this 'light-weight' and simple utility, you can create backups of Windows registry files to a location of your choice and then restore these files at a later date. You can also use the backups created by Regbak while running the 'Windows Recovery Console', making Regbak an ideal choice for all registry restore scenarios.

Version: 1.5
Supports: Windows 2000, 32/64-bit Windows XP, 2003, Windows Vista, Windows 7, 8, 8.1

Registry Compactor
The Windows Registry grows as data is added to it, but it never shrinks when data is removed. A bloated registry with a lot of empty space can slow down the boot time as well as performance. Registry Defragmenter and Compactor will rebuild and re-index your registry to eliminate structural mistakes and corruption.

Version: 1.6.1
Supports: Windows 2000, 32/64-bit Windows XP, 2003, Windows Vista, Windows 7, 8, 8.1

StartUp Guard
Monitor your system's auto-startup programs with this lean program. Startup Guard will inform you when new programs are added to the startup, in real time, and you can approve/disapprove the new entry. You can block worms, spyware, adware, trojans, and other virus type malicious programs that may affect your system by adding itself to run at Windows startup. It can also monitor changes to your browser home page and search page hijacks.

Version: 1.0
Supports: Win9x, ME, 2000, XP

Ram Optimizer
Optimize your memory (RAM) using this lean program and avoid application crashes due to low memory. This program monitors your memory and frees up memory if it falls below a certain minimum level. The program itself consumes very little memory - the lowest when compared to other such programs available. Ram Optimizer can also be configured to free memory automatically.

Note: Windows XP, by default, has efficient memory management methods and hence you may not notice any performance improvement while using memory optimizers. Almost all memory optimizers/boosters available on the market - both freeware and trialware - may prove to be inefficient for Windows XP and its successors. Such programs are recommended for 95/98/ME only.

Version: 1.0
Supports: Win9x, ME, 2000, XP

Tweak N' Tune
Tweak N' Tune is a "tweaking" program to fine-tune settings that are hidden in Windows.

Version: 1.1
Supports: Windows XP