I think that the majority of these applets were designed for people who know little about the hardware they are using - but I am not saying that all people who use them know little about their hardware.
Some hijack your machine, some are shareware, most drop bits all over your system that are there for ever doing God knows what, and many promise the earth and you pay the earth for them to do it. So, IMHO - the most you can do for yourself the better it will be.
I can't cover everything but for example -
- Backup - why not just copy and paste?
- Clean-up, Windows has most facilities built in
- Firewalls etc - again built in
- Browser cleanup - again IE6, FF etc all have good built in tools.
I use as few proprietory applets as possible but the ones I find indispensible are
- AVG Free Edition for anti-virus
- Spybot
- CCleaner
- HiJack This
- CWShredder
You will notice that the above are all free, all very good and most important are all used to combat internet infection. I do a cursory reg clean with CCleaner but deep cleaning I do manually using Regedit. I do not recommend using Regedit unless you know what you are doing. HTH.