I recently had my corporate-build laptop upgraded from Windows XP to Windows 7. The laptop in question is a Dell Latitude E4310 which came fitted with 4GB RAM- more than sufficient for 32-bit Windows XP, but the OS upgrade offered the potential to increase.
The laptop has two memory slots, originally both filled with a 2GB modules. For this upgrade I purchased 2 4GB modules to replace them. The parts arrived within a couple of days so the next task was to fit them.
The memory slots on the E4310 are located underneath and accessed by simply undoing two screws and lifting the flap. It was straightforward to release the clips to release the old memory and simply slot the replacement modules in in their place.
On rebooting the laptop kindly informed me on the POST screen that the amount of memory had changed, and Windows 7 booted up showing the new memory.
Interestingly there was one downside to this upgrade. When you increase the available RAM, the size of the hibernation file hiberfil.sys increases accordingly- when the laptop hibernates it stores the contents of the memory onto the hard disk so it can resume where it left off- the hibernation file must be big enough to store the entire memory contents. On many computers this would not be a problem, but this laptop came with a 64GB SSD drive so disk space is precious. Not necessarily a major issue, but a couple of versions of Call of Duty later and the C: drive is overflowing. Anyone else considering a similar upgrade may want to budget for a replacement, larger, SSD drive or (as I did in my case) make use of the USB/eSATA ports for additional storage.