Snazy casing with 5 fans, and a water cooling system.
Motherboard - ASUS A8N-SLI Deluxe ACPI
Processor - AMD Athlon 64x2 2.41 Ghz Dual Core (4800+)
RAM - 2GB (2x 1GB)
HDD - Samsung HD400LJ (400GB)
External HD - 1TB WD
Graphics - ATI Radeon HD5500 Series (1 year old) / Upgraded from Geforce 7900GTX (Broke)
OS - Windows XP Proffessional x86
This PC was top of the range 7 or 8 years ago and very expensive. But I stopped playing top end games on it a long time ago so had no need to upgrade it (have an xbox 360). But I still play the odd strategy game eg. Total War, FM + Portal 2 and things like that, and want to play some upcoming games like Sim City, Xcom, Rome TW2.
But the main reason to upgrade is that its incredibly slow at everything these days, loading a steam game can take 5-10 mins, even years ago it took 5mins to get into a team fortress game. And running anything makes it feel like its about to drop dead. And its faster browsing the internet on my iphone. (although i barely get 4mpbs speed at the best of times). My graphics card went a year ago so I replaced it with a modern budget one, and at that time reset and deleted everything, i barely have anything installed, 2-3 games and basic things like open office, abobe, and internet stuff.
So where do I start?, my budget is as little as possible in order to have a smooth running PC which feels new. I also want to upgrade to windows 7 64bit, but should I change my motherboard, and I have heard RAM would be easy update but which one and is it compatible with motherboard. And are SSD drives a good idea? Will i be able to run some of the games i mentioned with current graphics card and cpu? Also is poor broadband effecting slowness or is it my PC too.
Nikorr is right in that a superior PC can easily be built today; however it still doesn't sound right to have that PC take forever to do simple tasks. What kind of maintenance has been performed on the system (software wise)? If well maintained a PC shouldn't need a re-install every year but yours could be due for a re-installation of the OS. If you want 7, 2 GB should run it decently. To upgrade your memory you'd need to find DDR1, which by now is 2 generations out of date (you won't find it new but resellers might have it, try ebay).
Down loading is mainly internet speed, but on this old system, I would first check for thermal throttling, (the old thing is full of dust and getting too hot!). Blow out the case and heatsinks, GPU, all components very well with compressed air from a can. You can use an air compressor if your are very careful and turn the pressure WAY down, AND the compressor does not have water in the tank. This thing is probably due for a heatsink redo anyway, remove it, clean it, reinstall with new thermal paste.
In general, you need a good GPU and either a GTX 600 series or AMD 7000 series is a good beginning. Then I'd recommend a 4 core Intel IB CPU, 8GB of DDR3-1600, at least a 120GB SSD and a 1TB HDD with a Corsair or SeaSonic PSU. A good system is going to cost North of a $1,000.