❗ Help me with RAM

5750 is less powerful than the 5770, imo the 5770 is one of the best power / price cards out there right now.

Decent is at least 1280*1024 for 4:3 monitors (best would be 1600*1200) or if you have a widescreen (more common) around 1680*1050 (ordinary 20" / 22"). And I doubt the 5450 is "smooth".

@EDIT: yeah, should be okay
@EDIT2: the 5770 needs 1 slot to connect and then requires the space of 1 more slot / spacer lower down as well. The two dvi ports are there in case you ever want more than one screen (you can have a multi-screen setup, some 5770 cards even support the so-called "Eyefinity" - you can play a game on 3 monitors for an "ultrawide" display)
@EDIT3: If you have a "standard" sized case any ATX power supply should fit (practically every PSU)
@EDIT4: never get a faulty card, never use vga if you can use dvi

A fps comparrison of fps (frames per second) for a few cards, "normal" is 60fps, sometimes a game is playable at around 30+ fps but it won't always be smooth, real gamers usually want over 100fps. This is for Crysis at the two "standard" resolutions:



And here is the same game with some AA (antialiasing - a setting that will soften the edges of rendered objects / models so that the game looks better):




As you can see in the AA chart the 5450 doesn't even reach 10fps (completely unplayable) whilst the 5670 ("weakest" "gaming" card from the 5000 series) "rockets" to 30fps on the 4:3 resolution (some consider 30fps to be the lowest "playable" fps, but I really don't like playing at under 60 if it's a fps), but only the 5750 reaches 30fps on the 16:10 resolution (widescreen).

Now the 5770 makes another leap in fps and is therefore what I suggest you would get, but certainly not the 5450. Note that this is Crysis and it's set to high quality meaning that if you use medium quality or a lower resolution you would ofc get better, possibly even great performance at the cost of not-so-pretty graphics. Most other games like CA, CF, PB etc. should have more fps at high settings / some AA than Crysis because they're less demanding, but for nice quality, dynamic shadows, AA, AF and so on (read: nice graphics) in games like CoD you might really want to consider getting at least the 5670 if not the 5770.

19" widescreen's native resolution should be 1440*900 actually, right? Are you sure it's a widescreen (16:10) and not "normal" (4:3) screen?

And if it's a "small" res you should be ok, but dvi is usually better because it doesn't need manual setting of clocks and phases (read this). As for the sites I only buy new stuff (I really push the limits with my hardware, my last PC cost a tad bit over 10 grand euros) so I try to get the best deals with sites like: Scan.co.uk (UK), [url=http://geizhals.at/eu/]Geizhals.at (mainly Germany and Austria, does UK too though), Idealo.de etc.

Most probably, yes.

It seems like you don't know. And he couldn't have more than 2 gigs even if he wanted.