With 4 GB of RAM you already received enough power for current operating systems such as Windows 7, 8.1 or 10 and the well-known Linux distributions. However, different applications can benefit tremendously from working memory, which is why they can respond more quickly and require less calculation time.
However, we can offer not only pre-installed, used laptops with 4GB of memory, but also various memory modules, with which you can equip your current system. It can be already with little effort and at a low price to get more power, so you are prepared for new challenges.
Whether you use 4GB of memory as a single module or which memory technology you are using, this always depends on the particular system. Some desktop PCs can be upgraded easily with four 4 GB memory modules for a total capacity of 16 GB, while others may be able to use a maximum of two 2 GB DDR2 SDRAM modules.