There is a common problem with Windows COA stickers which are applied to laptop computers. The stickers seem to come in two types - plain paper or plastic coated. When a plain paper COA is applied to a laptop it tends to wear away in use until it becomes illegible. Sony for one, put a clear plastic film over the sticker to protect it.
I first tried easing of the complete sticker with a craft knife. This took ages and mangled the sticker. Later I developed a quick and easy method.
To remove the sticker for safe keeping,
1. Cover the sticker with a piece of thick clear tape ( I use polytunnel repair tape).
2. Run the point of a craft knife around the edge of the sticker, and peel off the excess tape.
3. Ease up one short edge of the sticker/tape until you have a complete strip clear of the case.
4. Peel off the complete sticker from side to side, it should lift off the top printed layer in one go leaving most of the base layer behind
5. Apply a little white PVA glue to the back of the sticker and apply on to a piece of plain white paper. Rub between finger and thumb as it dries to flatten out.
If your sticker is already too far gone - I recommend downloading BERLAC ADVISOR. This is a great free program that will recover your installed COA and the Keys for most of the programs installed on your PC.