For Your CD key,
Install Everest (A Benchmarking Software)
You can find all your system information here, whether its software or hardware.

Its a trial version (I think) but it does do the trick
Download from here:
http://www.lavalys.com/
For Back up
Acronis True Image is most recommended
http://www.acronis.com/
Again, its not free

(Trial Version)
But it should help
For maintaining PC
Install a good Antivirus which does not hog RAM
Kaspersky, NOD32, AVG, Avira are useful here (Dump Norton And McAfee, its a bunch of cr@p)
Secondly,
Clean your PC of obsolete and useful files using Ccleaner
Thats it.