For both (but I suppose you're talking about the desktop), sorry, that's an integrated graphics card too, not a standalone.
Noticeably cheaper that way, but can't move it around sadly.
Also, not THAT great, to be honest, but at that total pricetag, you can't really afford to be picky.
Hmm, also, that's weird... it's almost same processor your machine has (2.7GHz Athlon dual core 64 bit), just a slightly newer generation (your machine has the 65nm version from early 2007, this one has the 45nm version out in 2009)... so you won't get that much extra performance from the processor (but it will almost certainly eat less power and have less cooling problems).
The graphics card though (integrated 6-series vs integrated 9-series), that's a significant improvement, and you should really see a big gaming performance increase.
Everything else though, it will probably work exactly the same way it does now, not one bit better.
Anyway, how come you don't have a 64-bit OS version installed, why the 32-bit version ? All 32-bit apps should run just fine on a 64-bit OS, with minimal or next to no degradation.
Also, that could be the reason you only "see" 3.5 GB of RAM, otherwise you would _probably_ see 4 GB (unless that's 512 MB of shared video memory out of the total 4 GB installed, but with a 6-series, I find that a bit odd, 256 MB or even just 128 MB would be much more common).
Now, you COULD splurge a bit extra and get something like this:
True, it's 550$ (at least no shipping charge), but for that you get (compared to the one listed for 400$+shipping):
* AMD Athlon II X2 dual core 2.9GHz - the newer 45nm version, so at least you get a bit more oomph for everything and less heating issues
* 4 GB of DDR3 of non-shared memory (as opposed to 4 GB of DDR2 that shares memory with the integrated card), and you will feel the difference here too
* a MUCH better video card compared to any of those integrated ones, a NVIDIA GeForce GT220 with 1GB of standalone RAM (the card itself is also a standalone card, so you can move it to the next machine) - it's not an awesome graphics card (it's actually quite low end), but it still beats those integrated ones performance-wise hands down
* a slightly smaller HDD (500 instead of 750 GB, but really, it's not like you even need 500)
However, if you really want to even begin to future-proof your machine for gaming, I seriously doubt you could go lower than 600$, preferably even more.
For instance, at the time being, I'd call this one as being pretty good as far as price/performance goes:
Sure, it's 610+25(shipping)=635$ vs the one above at 550, but what you get improved (RAM and HDD is the same) is this:
* AMD Athlon II X4 630(2.8GHz) - that's a QUAD core processor, those extra cores really help in newer games, so, really, it's worth spending some extra
* ATI Radeon HD 5670 512MB video card - true, it has "only" half as much RAM... however, it completely obliterates the Geforce GT220 performance-wise, it's more than twice as fast... so, yeah, you won't be playing with ultra-high texture details (you'll have to "settle" for regular high), but you'd be getting a so much better FPS that you won't regret it (and BTW, the retail price difference between those cards is around 50$ higher for the HD5670 compared to the GT220)
Sure, it's "a bit" above your budget, but I'll bet it will be really, really worth it in the long run.