EASUS Partition Master Home Edition is a freebie which enables you to not only partition without data loss within Windows, it also boasts partition and disk copy wizards too, making it easy to clone hard drives or quickly back them up.
Autoruns

Windows' built-in msconfig tool is all well and good, but if you want complete control over what starts with your PC, then Autoruns, a free tool from The Artists Formerly Known As SysInternals, is an essential addition to your toolkit. You can delete as well as disable start-up items, plus access other start-up zones too.

ISO Recorder

ISO Recorder is a fabulous tool which makes it easy to burn discs from ISO images downloaded from the internet (such as Linux distributions), but it's also able to back up uncopy protected CDs and DVDs to ISO format too.

DAEMON Tools Lite

Tired of constant disc-swapping or hunting for lost DVDs? DAEMON Tools Lite creates up to four virtual CD/DVD drives that can access disc image files (including ISO and IMG) as if you'd inserted the discs themselves. Oh, and it's quicker than accessing the real thing too.

CCleaner

There's only so much crap that Windows' own Disk Cleanup tool can handle - if you want a tool that does a more thorough job, CCleaner is that program. Use its Registry cleaning tool with care, though.

Free Registry Defrag

You can't rely on Registry cleaners to always get it right when cleaning out your Registry. Deleting so-called "problem" entries is only half the job anyway - Free Registry Defrag won't delete anything from your Registry, but it will compact and defragment the contents of your Registry files so they perform quicker. There's an element of risk with any Registry cleaning exercise - (visit regrecovery before you begin, just in case.)

Defraggler

Most defrag tools will only let you defrag entire partitions or drives; Defragglerlets you analyse your drive and then pick individual files and folders to defragment - perfect if you're running on a tight schedule.

Ultimate Windows Tweaker

Vista users casting a jealous glance at XP's TweakUI PowerToy can stop being envious: the recently released free app Ultimate Windows Tweakerpacks in over 130 tweaks into a single 380KB executable file - no installation necessary.