OS: Microsoft Windows XP Professional 5.1
Processor: Intel Core2 CPU 6300 @ 1.86GHz (2 CPUs)
Memory: 3582MB RAM
Hard drive: 141 GB
GFX Card: NVIDIA GeForce 9800 GT

what do you think of it?
good or bad?

Pretty bad, the processor if anything bottlenecks the graphics card but the graphics card isn't even that good to begin with.

its 3 years old (or two not sure)
in the time it was good, but 2 years is a lot of time in IT
it can still run every game tho, just some only on min-mid spec

I thought the card wasn't that bad, but you sir have one old processor

lol'd at the processor.

Man you need an upgrade.

The GFX card is pretty nice, but with the backdrop of a 1.9 GHz processor and 141 GB hard drive, it doesn't look good.

Invest in a new computer.

Actually this is not that bad for most games, anyone who said it was bad can go away
Also if you like Lume stated the processor would bottle neck the GPU your only JUST correct, however the amount of bottle-necking wont be that large, most games barely use 2 cores, however that CPU has a rather small cache and low clock speed, other than that it's fine. Conversely if you use this computer for video editing your fucked, I do believe it was never stated that this was a gaming computer.
The RAM confused me a bit, how do you get 3.5GB's of RAM? That must be some really odd combinations, 3x1GB + 1x500MB?
The GPU wont run every game, but I'd have still recommended that graphics card about a couple of months ago (and I in-fact did someone around here) as it's cheep and powerful.

Lastly I'm surprised no one mentioned explicitly windows XP, this I would change. Upgrading to windows 7 would give that computer a new lease of life.

Recommended upgrades without replacing computer: (Almost in order of importance)
OS: Windows 7.
RAM: switch all that for 4GB of branded RAM, RAM is cheap nowadays and this would improve stability and performance.
CPU: Core 2 Duo at around 2.6 to 3.2GHz.
GPU: Unless you need more games performance your fine.

I think he's got 3.5GB of RAM because his OS is 32 bit. He may actually have 4 GB but the OS can't see more because on 32 bit the max ammount of memory is 4 GB, but that applies for the GPU memory as well (I believe it's the 512mb version).

Also, the GPU isn't THAT bad. I have it and it still can play most games at mid-high settings only with AA down a bit (2x/4x) at 1440x900.

Also, he could get a 500GB HDD as they're not that expensive and tbh, 160 GB is not that much.

He wouldn't need it. He still has over 100gb left. Just buy a new HDD when you actually need it, if you don't then it's just a waste of money.

Having said that when you do buy a new hard disk drive your looking at 500GB to 1TB as the standard size for good GB/dollar ratings, also check your disk is still in working order with some disk checking software (I don't know any good software to recommend for this maybe someone else can help there) as you may have a few failing segments with a very old HDD, limiting performance, stability and size further. Oh and something not many people seem to know, higher capacity per platter = faster drive, so a 500GB (1 platter) or 1TB (1/2 platters) would be around 3 times faster than a 1 platter 160GB HDD, where the speed refers mostly to the seek time / overall latency.