Here's my Rig,

MSI motherboard
Radeon 9550 (CATALYST 5.5)
512mb DDR ram
cd rom52x (32x burner)
AMD Athlon(tm) XP 2200+ 1.79GHz
40 gig samsung (not in use)
110 gig wdc wd400
300w power supply

In 5 weeks i will have enough mony for these upgrades,

http://www.newegg.com/Product/Product.asp?Item=N82E16813131510
that my ASUS A8V DELUXE Socket 939 VIA K8T800 Pro ATX AMD Motherboard
Same video card
http://www.newegg.com/Product/Product.asp?Item=N82E16820144321
GeIL 1GB 184-Pin DDR SDRAM Unbuffered DDR 400 (PC 3200) GB
Same cd rom but i'm also getting a NEC Beige 16X DVD burner
http://www.newegg.com/Product/Product.asp?Item=N82E16827152039
As for the CPU It's a AMD Athlon 64 3000+ Winchester
http://www.newegg.com/Product/Product.asp?Item=N82E16819103501
Same hard drive

In another few weeks im getting 500 watt powersuply
http://www.newegg.com/Product/Product.asp?Item=N82E16817182009

First up Do yaw agree or disagree with what i'm going to get for my rig?

Last I Read at certain web pages (I forgot what pages) That you could indeed over clock this kind of video card. If so how do overclock it?
... I mean is it is the system bios or can you do it from windows?
or would I have to upgrade my BIOS, because in that case i Can just wait untill i get my new parts.
I need some advice. ... (system Memory)this is bit of topic but what is the different typs of speed in memory, what is the timing, and whats the difference between Registered andUnbuffered memory.

Can anyone help me with anything I said? ... Overclocking, ... Or even the memory?

One other small qustion ... could anything bad happan if i install new drivers (video) over the old drivers? Does the system work better if you take the old drivers off than put the new drivers on? Or ... How does that work out?

Ok, to oc your card you dl some utility like rivatuner(guru3d.com), and it has settings to help oc. I think some 9550s can be soft modded to 9600 cards, but I don't know what that involves.
Edit: I looked and it seems that 9500's are the moddable cards not 9550. It seems that some 9550's can oc to 9600pro speeds though.

I wouldn't get a rosewill psu, just because it's an off brand, check out antec or enermax.
Here's a good psu.
http://www.newegg.com/Product/Product.asp?Item=N82E16817103464
Here's a good psu guide.
http://hardforum.com/showthread.php?t=792566

I think you haven't gotten many replies because oc'ing topics are supposed to be in the modding thread.(it makes sense to me though for it to be in the video section, it is about your video card).

I haven't uninstalled my drivers when I updated. I just installed the new ones(maybe I'm doing it wrong, I haven't had trouble though). That's with a nvidia card.

There are basically 2 types of memory now. ddr and ddr2. Amd systems don't support ddr2 yet, but intel can use either(whichever slot the motherboard has). There are also different speeds like ddr400, ddr333, ddr266, ddr533, etc. You want the fastest your motherboard can support(or faster if you overclock). Timings are like 2-2-2-5, which is for fast ddr memory, and 3-3-3-8 for slower memory. Sometimes the mfg just lists the cas value, the first digit, so 2-2-2-5 is cas 2. Ddr2 has higher latency values than ddr. It can be cas 3 or 4. I think registered memory is for servers, but I'm not 100% sure about it.

Thanks you helped me. ^_^ I'll see about the clocking should be in another thread.