Laptop shows 3GB of RAM memory installed but only 763MB usable

RAM memory problem: HP Laptop shows 3GB of RAM memory installed but only 763MB usable

My HP G62 laptop PC runs Windows 7 Home Premium. After I started using Photoshop Elements 10, it slowed down very noticeably, so I had a look in System Properties (enter the word system in the Start =>Search… box and click on the System link under the Control Panel heading). It shows 3GB of RAM memory installed but only 763MB [about three quarters of a gigabyte] usable. The Windows and HP memory-diagnostic tools find no fault with either of the modules. When I press the Ctrl+Alt+Del key combination and choose to open the Task Manager, when no programs are running, the Performance tab shows the Physical Memory around 760MB with the graph running at the very top. When I click on the Resource Monitor button, the Memory tab shows 635MB in use and 2310Mb hardware reserved. I tried removing the 1GB module. On startup, only the power light lit up – no boot. I moved the 2GB module to DIMM slot 1 where the 1GB module was and the laptop started up. The Caps Lock key’s LED came on but the system did not boot. When booting with the 1GB module it still shows 763MB available, which is probably about right.


My most problematic self-built desktop PC wouldn’t boot and I couldn’t even get into the BIOS, but the processor cooler’s fan spun. I used floppy disks to test the memory with a few reliable memory diagnostic tools on them, which all passed the memory as being fit for purpose, so I swapped the power supply, the graphics card and the motherboard with components that worked in other PCs, but without success. I tested the processor in another PC. That left only the memory.

At that time, I didn’t have any DDR3 memory to swap out, so I used the Crucial Memory Advisor on to tell me which memory configurations were supported by the make/model of motherboard, ordered the memory I wanted and the system booted up from the Windows installation disc immediately after it was installed. What a lovely feeling it is to see a self-built computer boot for the first time. I sent the incompatible memory back to the vendor (not Crucial, the vendor that supplied all of the other components). Therefore, memory can pass several tests and still not function.

Your 2GB memory module is almost certainly faulty and should be replaced, or, better still, get the best configuration of memory modules that the laptop supports.

You didn’t supply the exact model number for the HP laptop, but the G62 series of laptops support dual-channel memory configurations, so better performance will be achieved with an identical matching pair of modules working in dual-channel mode.

Note that the DIMM memory slots are usually colour-coded to indicate which slots should be filled in order to run the memory modules in dual-channel mode. For example, the first and third of four slots may be coloured blue with the second and fourth slots coloured white. You would install two identical-capacity memory modules in the blue slots (first and third) first and another two identical-capacity modules in the other two slots in order to have them working in dual-channel mode. If you have modules with odd capacities (e.g., 2GB and 1GB), you would install them in the first two slots, because non-identical modules cannot function in dual-channel mode. The motherboard’s user manual provides the information about which capacities of module can be installed in the DIMM slots and in which configurations. If you don’t have a manual, download one from the motherboard manufacturer’s website (,,, etc.) It is usually in the PDF format, which requires a free PDF reader such as Foxit. If you want to find out the make/model of the motherboard without opening the case in order to determine which website to visit, you can use CPU-Z from

I would buy a 4GB upgrade kit (2x 2GB) and keep the 1GB for a emergency or sell it on eBay. If you have Windows 7 Home Premium 64-bit version installed, or intend to install it, a 6GB or 8GB kit can all be used and should future-proof the laptop for several years. A 32-bit version of Windows Vista, Windows 7, Windows 8.1, Windows 10 can only use approximately 3.5GB, so there is little point in installing any more than 4GB on a 32-bit system.

About Eric 275 Articles
I am an experienced PC technician who has been the owner and sole writer of the PC Buyer Beware! website since 2004. I am learning all the time in this very dynamic, ever-changing field.