I have a laptop with 4GB DDR3 RAM and now want to double the RAM but I have now looked on the Internet and they look somehow bigger and I wanted to ask whether the DDR3 is always the same size or there are different ones?
More ram won't do you much good with this device. This is a pretty old box, a new purchase is appropriate.
You need the so-called "SO-DIMM" RAM. Just google it. If necessary, enter the serial number of the other RAM stick.
There are different, the best thing to do is to simply look for the specific model of your computer type or your motherboard
Also check whether 8Gb can be addressed at all or is supported.
Yes it will
You should find it here:
https://www.ebay.de/...GB&_fsrp=1