OK, now I know this is bound to be a very stupid question indeed, but could someone please explain what Major/3rd means when talking about RAM?

Many thanks in anticipation!

Major means: the bigger (supplying company-)names, like Crucial/Kingston
3rd means: third party, i.e. other (not so well known) suppliers of perhaps the memory chips, like Samsung, Siemens

Thanks! That makes a bit more sense now!!

Does it need to be put in a certain slot? Or is that just a myth?

Depends on your mobo AND on the type of memory.
If you have 1 stick, slot 1 is appropriate.
Matched pairs (normally more expensive) go into matching slots as per mobo-manual.

That's great. Thanks so much for taking the time out to explain mate. Much appreciated!

For the record...it's better to go with top brand name RAM - skiming on the memory and getting something cheezy will bite you more times than not, in my opinion.

I have had issues when mixing brands, especially the cheaper ones...but I definitely will defer to your expertice Miclantecuhtli - from your prior posts, you definitely know what you are talking about. I'm just sharing some experience that I've had...I guess when you get burned, you kind of get set in your ways is all...

Well all I can say is that is is good to be able to benefit from other's experiences. Thanks very much chaps.

Not a problem...let us know what you decide to do and what the outcome is...and remember - I only offer advice from my experience, but there are always quite a few valid opinions out there, so play the field.

Sorry, I should have given you the set up when I asked this question. Mobo: A7N8X-X REV 2.xx; CPU: Athlon XP2500+. I have 512Mb of indeterminable RAM, an ebay buy. I have a couple of probs with the setup which, from other threads, seems to be down to the RAM (eliminated every other likelihood) so I wanted to buy some new RAM. What I will do, I think, is buy 2 x 256 of Kingston. I shall report back! Once again, many thanks indeed.

RAM

Check a few places and compare prices as well, before you plunk down your hard earned cash...I think a couple of the bigger online vendors are having sales on some of their branded RAM (Corsair and Kingston to name a few)...also, you might want to see if you can get 1 stick of 512 cheaper than 2 x 256 (you never know)...either way - let us know how it works out.

I will do that!

Do not buy value Kingston Ram if yu plan on overclocking. It does not overclock well. Corsair is better for overclocking than kingston. I use Crucial RAM in everything I build, but I do not ever Overclock.