Your specs are to weak for PS2 emulation, certain games may work as you pointed out above but certain {and by that I mean almost all} games will have considerable lag...
The minimum can pretty much be ignored in this case, I have Intel Core 2 Duo @ 3 Ghz, 4 Gb RAM and a 8800GTX and I still get occasional lag in certain games mainly Valkyrie Profile 2 Silmeria but I have heard certain games are more demanding than this especially the final fantasy and god of war games and that valkryie is slightly buggy in the emulation side of things.
Your GPU and CPU are below the recommended specs and I would also consider getting more RAM as 1 Gb is cutting it really close and is below the recommended in vista and win 7, also your CPU doesn't support SSE4.1 which apparently made the emulation substantially smoother {or so I read on the forums}.
This is quite a good thread on their forums laying out what you can expect with your specs and suggestions for various speed hacks and such to make lower speced rigs run faster {be warned through it's 314 pages long and you may have to do some digging to find info relevant to you}, apparently Final Fantasy X is a very good benchmark for what kind of performance you can expect in more demanding games {if you have or can obtain a copy} it's worth firing it up to see what performance you get.
Link:
http://forums.pcsx2.net/Thread-Sticky-Will-PCSX2-run-fast-on-my-computer
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I know there are many tutorials online..believe me I've been through a number of them,but I want to hear from someone who actually has it running smoothly and what version they used?
