I have a brand new Packard Bell I-Media X2415 desktop with 3Gb ram (a 1gb and a 2gb). However my vista experience rating is only 4.5, based on the number of memory operations per second.

I’ve seen people with scores over 5 with only 2Gb ram - does this mean the PC is just loaded with rubbish components or is there an explanation? Maybe there are problems because the two rams are of different sizes?

And how reliable is Vista Experience as a means of testing your computer's potential performance?

Answer:
The reason you have such a low score is due to your configuration. I’m assuming these are DDR2 memory, well in order to get the dual channel support you have to install them in identical pairs. In other words you would have to install 2 1GB modules and 2 512 mb modules for your 3 GB, if I were you I would just purchase another identical 2GB module to pair up with your other and take out the 1GB module. This is the configuration you should have and most companies install when they sell 3 GB systems. You never put DDR2 memory in as single modules, you have just basically halved the bandwidth and speed of your memory because you’ve lost the dual channel support.

I know this from personal experience since I tinkered with different configurations of memory on my Vista computer and then did some research to find out why I was having the same problem. Older memory that didn't rely on this technology didn't require you to install in pairs of course even older technology required you to install in quads. (30 pin simm modules)

Answer:
It might just be the fact of the computer and it's hardware.

Some personal do tend to perform superior than others, even if they have the same or superior stats. I’ve a friend who has the same stats as my Personal computer (which is 1gb), but his is WAY faster than mine! It's probably just the hardware is not the most sophisticated. I could be wrong of course ;)

Or that it could be that the site is unreliable =)

Answer:
It's not the quantity of the RAM, it's the quality. Just because you’ve 3 Gb of RAM doesn't mean that it's going to go super duper fast. You need to get _good_ RAM to go really fast. The clock speed and the timings have everything to do with the speed.
Answer:
Mine is 6.1 but i have a Quad core processor and nVidia 8800GTX 768Mb with 3Gb ram