You can probably find the manual for the netbook online and it will include step-by-step instructions for disassembling your computer. Also, I highly recommend getting small containers or labelled sticky notes to put the varies sized screws in/on, I've taken apart a few laptops and doing this makes it a lot easier when putting it back together.
Also run a disk defragmenter, and like ScOuT mentioned, CCleaner can clean out your temporary files, unused registry items, etc., but make sure to create a backup using CCleaner before doing any cleaning.
Cleaning out registry keys doesn't really give you a performance boost, however, if you do "clean" out your registry, make sure to do it before you defrag your HDD.
Use
ATF cleaner or
TFC instead to clean out your registry (they are considered more safe, but I haven't used ATF-cleaner just found it on the web as a good registry cleaning program), but make sure to create a backup first, because you could end up damaging your PC.
Actually I'm not sure if TFC or ATF even clean the registry, but they clean out temp files, cleaning out the registry isn't even that important anyways, unless it really bugs you that there are orphaned registry keys in there and you manually go through your registry regularly, which I doubt you do.