Upgrade this system or go all new?

My first question would be, what do you use your system for?

4GB of RAM should be enough for most any common PC tasks. It is also enough for some light gaming. So if you are planning to stretch the life of your PC a little bit, this may be a place where you are fine. If you are a gamer, your GPU would be the first place to upgrade. Your motherboard has a PCI-E 2.0 x16 slot so you could run any modern video card. The new cards are PCI-E 3.0, but it is completely backward compatible with 2.0 and even 1.1,etc. The only difference is the transfer speed. However, most of the current video cards do not even saturate the PCI-E 2.0 x16 bus so you are fine.

Let us know what you use this for and we can help guide you.

I'm sorry, I should've been clearer from the start. I am mostly gaming with this machine, and of course the usual internet browsing. How would you upgrade to make the pc faster, so it doesnt slowdown every so often and freeze sometimes?

I would suggest going new especially with the core 2 duo. But if you are looking for a quick boost to performance on the cheap Windows 8 has been shown to really put the zip back into older systems especially because of the resource hog Vista is I think you should start with that and I think it is only 40 bucks right now more or less.

I am currently trying to upgrade my rig as well, tho I can tell you from experience that one way you could "boost" your performance right now is getting rid of Vista, also get 64bit if your machine is capable of running 64

Vista is a resource hog and another possible down is that your running 32-bit which is usually capped at 3GB of RAM being able to be used, so you have 1GB just sitting there doing nothing

I wouldn't suggest Windows 8 right now, being a new OS its having issues with some programs/games. Win 7 is pretty solid and uses less resources then Vista and is probably cheaper then Win8, I got my Win 7 Pro for only $30 back in the summer during a deal on New egg

Vista with all the service packs is only maybe 3% slower than Win7, so that is very unlikely to be the problem. Now a clean install might help, but I wouldn't spend $100 to jump to Win7. IF he wanted to go 64 bit, you can use a 32 bit key (or better to just use an activation backup app) with 64 bit, you just have to find the 64 bit media. Or Win8 is only $40 upgrade, so that would be the way to go.

Now I don't really think it is worth sinking any money into that system. I'd probably go ahead and just update the whole system at this point to something like an i5 or a FX-8320. YOu might be able to reuse the case, power supply and drives to save some money, but the main guts are all going to be obsolete at this point.

I would also recommend putting your OS and main apps on solid state drive on a Sata III port if you want to eliminate stutter and pauses. It's amazingly fast and you never have to wait for a drive to spin up or park.

I still don't understand the hate for vista. I ran Vista for 5 years or so and never once had any issues and am an avid PC gamer. I just recently upgraded to Windows 7 specifically because I bought an SSD and wanted the TRIM support. I really have not noticed any difference in gaming or performance otherwise between the two. Vista just got a bad rap and Windows 7 is really just Vista 1.1. They just turned off some features and added support for a few things and some bells and whistles. That comment was straight from a Microsoft rep at work.

The RAM is a concern and you loose some of your 4GB because of how it addresses memory and specifically video RAM. When you run 64 bit, it maps around that issue. However, for the best bang for your buck, you could upgrade your video card. Sure your Core2 Duo will hold you back a bit, bit I still know guys gaming day to day on a C2D without issues. So I would plan for a new system, but your quick fix is a video card. The 9600GT is pretty old and just won't stand up to current games.

Windows 8 will not do much for you besides frustrate you on having to learn the new layout. Without a START button I really disliked that it took away a basic function for me to navigate my system. Sure for a general user 8 might be fine, but I like to be able to easily get to administrative functions of my PC.

If I get a new system like http://www.tomshardware.co.uk/forum/368997-13-good-gami..., will I need to replace the system again in 3-4 years or is it possible that a simple upgrade will make the PC last some longer than the previous one?

There is no such thing as a "future proof" computer and 3-4 years is all you can really expect for it to stay relevant, especially if you are a gamer or high power user. For general office, even 8 year old computers still do fine.

So there is no reason to go more to the high end side of systems than to go with a "just good" one except games will run at better settings with better fps (which will not be noticable)?

It depends on your style. You can overbuy and make it last longer, which gives you insane performance up front and merely acceptable performance in years 4-5. Or, you can buy medium-high end every 2-3 years to get more even performance, but never be "on top" with bragging rights.

And where would you say the system is I described in the topic I linked? A think I did change to it was the case, which I replaced with the Corsair Carbide 500R and I left out the CPU fan because I will not be OC'ing.

That's probably today's equivalent of your current computer. Your current build had a pretty high end GPU and CPU when built, but not the best.