I think there are some very good (but basic) points of view here and most of the essentials are covered. If you have speed issues with your PC upgrading the amount of RAM MAY
help but it isn’t a miracle cure.
RAM is very cheap and very easy to source and install so therefore is a recommended upgrade.
People have mentioned Vista is memory hungry but how hungry?
To give you an idea a fresh install of Vista Ultimate 32bit with Office Enterprise 2007 but no other applications consumes about 1.3GB or RAM. The most important thing to take from this is if you have less than 2GB of RAM and are running vista you do need more!
Although 64bit is capable of realising additional memory up to 32GB (I think) it is important to mention 64bit compatibility!
No one has mentioned the problems 64bit software can cause if you don’t have 64bit drivers!!!!! This has to be a major concern and unless you are certain both all your software and hardware is compatible (most brand new stuff is these days) please avoid it like the plague.
General advice: IF YOU DONT HAVE A ROCK SOLID, LEGITIMATE REASON TO UPGRADE TO A 64bit OS THEN DONT!
Other factors affecting the speed of a PC;
BUS and HDD speeds;
Although it's great to have huge super fast RAM how does the data get there in the first place? 1, 2 or even 4GB of space isn’t huge so the image data can’t live there indefinitely. The reality is the data on the HDD, in relative terms a very slow storage device. if you are fortunate to own a SATA 2 drive spinning at upwards of 10,000rpm (most people don’t), once the data is read super quick how is it then going to get to your RAM?
This leads on to by far the most significant component of any PC the motherboard!
Someone touched on this before that unless your motherboard has the capacity to move data around at high speed and is compatible with the technology you wish to use DDR2/DDR3 etc it is irrelevant what processor, RAM or HDD you have.
Processor: speed test shows that Quad cores are significantly faster than Dual core equivalents however based on my experience it is often better to go for slower clock speeds as the latest releases are exponentially more expensive. A 2GHz quad core is phenomenally faster and more powerful than a 3GHz P4 of about 2 years ago. If you cannot justify the additional cost of a quad core processor then a 2GHz dual core equivalent will suffice.
I don’t want to sound depressing but if you have a slow PC, unless you have less physical ram than is required (approx 1GB on XP and 2GB on Vista, excluding applications such as lightroom with huge RAM consumption) (knows as paging, when data that would normally be held in fast RAM has to be swapped backwards and forwards onto a slow HDD due to space issues) it is unlikely adding another GB or so will to blow you away
One last note, there is a limited number of "slots" for ram to be fitted this can vary depending on manufacture. If you only have 2 "slots" and both are filled with 512MB ram giving 1GB total, buying an additional 1GB stick isn’t going to give you 2GB as you will have to permanently remove one 512MB module that currently occupies the space. Please check this first to avoid disappointment.
Sorry for the long post but I hope it helped.
<- really there not that bad. £500 will buy you a perfectly good machine for photo editing as long as you’re sensible and spend it on the essentials.
If you have any further queries please feel free to ask, I’m an IT engineer and you guys have certainly helped me with my photography that’s for sure.