Where are you actually reading these memory settings? Is it in BIOS or the operating system?
I would assume thet it is from the operating system as in bios you should normally see the full 8GB available. If you are seeing the 3.49GB in the operating system then that is normal. This means that you are using a 32Bit operating system and this is a limitation of the operating system, there is nothing much that can be done if you want to keep your operating system.
Best solution is to re-install the operating system but this time use a 64Bit version of operating system installation as 32bit version does not support 4GB or more memory.
Hope this will be useful to you.