
Windows Vista its just like anything else if you don't do maintenance on it, it wont work properly
and there are a few hints to make this happen first of all lets start by the basics:
Ram: the more you have the better but keep in mind that only 3GB  of ram is what you will see under the 32bit OS while the 64bit will let you go further so take a pick and remember that all the cpu's out there are 64bit so the only thing you need to do is get compatible drivers for it.
GPU: [Graphic Processing Unit]- now you either have an IGP[integrated graphic processor] or you bought a desktop from any store that comes with a decent GPU, now if you have an Intel IGP forget it that won't cut it that's not gonna help you a lot , there are 2 brands out there ATI and Nvidia choose what you want and do your research on both, you also have to look at how much Vram this gpu is packing 256MB ddr3- 512MB ddr3 and so on , the more the better but go with your budget in mind , don't forget to stay up to date on drivers its very important since if you have issues with certain applications updated drivers may fix this for you.
CPU: now we have Dual Cores and Quad Cores and 2 brands to look at AMD and Intel you can easily go to newegg and read on the reviews and make a decision  if you are building a PC by yourself or you can decide what desktop fits your needs if you need dual or quad , honestly if you have a single core CPU there are cheap quads and dual cores out there and it will greatly improve your overall system performance.
There are more parts to the PC than the ones described above but those 3 are really important 
and of course you also gotta make sure that you motherboard supports it.
Now lets talk about Optimization  for your OS since you have a better understanding of what you have under that system, there are some programs that are designed to help you with this task cleaning up registries , speeding up your system you name it and so many of them trying to catch your attention indeed , one program that i love is Tune Up Utilities 2009 now if you get this program use it at your own risk, this program will basically offer advise on what is running on your background in other words when you start Task Manager you see so many things running but you don't have an understanding of what you can shut off and what needs to stay on for the OS well this program makes that easy for you , it also cleans up your registry now here you really have to be careful if it deletes something that is not supposed to your OS might not start at all also keep in mind that the program comes with a back up utility but what good is it if your OS cannot start right and that's when you fully understand that having a recovery disc is also important or a copy of a Windows Vista  Disc  so lets say your OS does not start you would basically press F12 and choose the boot device and that would be your DVD drive where you would have the OS disc already inserted  and once you are under the menu  options you would choose repair since you are not doing a clean install but repairing problems in your OS.
Something else that is very nice is lets say that you have 2GB of ram in your system then raise your Virtual Memory to double that amount , Click on Start go to Computer , click on    System Properties  then click on Advance System Settings , click on Performance  settings tab you will see the following Visual Effects ,Advanced and Data Execution Prevention choose Advanced
here you will see Processor scheduling which should be already under programs  now further below you will see virtual memory click on change once there click on custom size so lets say you have 3GB then 6000 would be the number on initial size and maximum size once you change it click set and it will ask you to reboot your PC do so at this time. 
Its also important to keep your Desktop shortcuts to the bare minimum and the same goes for how many things you have running at the same time well that's all the advice under this one i will post more later on when the time is right i hope that this is of some help to some of you and remember that a PC can be a headache  but if you do some troubleshooting you will find your problem and of course you have google to search for that specific problem.