If you are going to run Vista 64 bit then I would install 4GB of memory. I am running 4GB Crucial Ballastic Tracer PC-8500, 1066Mhz on Vista Ultimate 64bit and the operating system along with other software are using 1.5GB at idle. Just my opinion!!!!
Can you get by with just 2GB? Yep, you sure can. At this moment Vista64 with just a couple browser windows open, several gadgets in the sidebar hanging on the monitor and a couple background trash programs running I am using about 1.5-1.6 GB of RAM.
Will you want to upgrade beyond 2GB? I suspect everybody eventually will. Having power at your finger tips is cause to use such power. Before long everybody will be like me and will have dozens of programs running simultaneously.
By the way, I have 8 GB of RAM. Not bragging. When I get my web & photo editors cranking up and have TV running on the monitor in the background I am routinely hitting 4.2 to 4.5 GB of RAM usage and have already seen 6 GB being sucked down. Like I said, having power available is soooo nice.
If you decide to go with 4 GB I would buy 2x2GB sticks rather than 4x1GB.... the cost differential is not that great and your upgrade path is cleaner.
If you're a gamer and intend on running some of the latest RTSs, and/or Crysis, etc, then more than 2GB of RAM would be a good idea. It *is* possible to go past 2GB of RAM usage in these games under certain circumstances, even if you're not doing anything else at the same time. Therefore having more memory available would help.
If you do Video, then you don't need any of us to point out that you need all the RAM you can get.
If you routinely multitask lots of windows, then you'll want a dual core CPU.
If you game and video at the same time, you'll gain benefit from running a Quad instead of a Dual Core, plus the aforementioned extra RAM.
Vista 64 will run just fine on 2GB of RAM. But it'll readily use more if you care to run the apps that'll take advantage, and DDR2 is cheap.
I've just built a pc with Vista Ultimate x64 O.S. and 2 GB of DDR2 800. It currently runs on an early 3.0 GHz Pentium D until I replace it with a Q6600 cpu tomorrow. I noticed that using onboard audio and video and viewing live tv in the Media Center program uses all but 13 MBs of system memory in taskmgr......sometimes even reads 0 available RAM. It seemed to be running ok but, I had a couple more sticks of the same memory so I added them and the system became somewhat unstable with the cpu reaching 90-100% for the same use that 2 GBs RAM was showing 30-40% cpu use! Instead of improving the operating of the pc, doubling the RAM made it unstable. I went to Windows Update and it immediately said I needed an x64 update "for potential instability-system freeze problems". That sounded like just the ticket, so I installed that update. No help.......system still unstable. It's possible that utilizing 4 GB of DDR2 800 with an older cpu that only runs at 800 MHz is what is causing the audio/video skips, freezes, mouse freezing etc. I'll know more when I install the quadcore tomorrow. I have removed the 2 extra 1024 MB RAM sticks and it is working fine now, albeit almost out of memory LOL! I sure hope 4 GBs of RAM will work with the better processor, I was counting on using that extra memory with Vista x64.
I can't really talk about 64 bits. Having XP 32 bits and Using 2 Gigs of ram and no paging file I never ran out of memory. The worst usage was 1.5 GB, running C&C 3 and Serious Sam II at the same time.
Still, 4 GB is the future, I'll soon go to 4 GB's of ram but I'll migrate to 2x2 GB. I don't like 4x1GB.
I've just built a pc with Vista Ultimate x64 O.S. and 2 GB of DDR2 800...... I sure hope 4 GBs of RAM will work with the better processor, I was counting on using that extra memory with Vista x64.
New - Some Mobos don't like running 4 DIMMS at their rated speed. First thing to do is bump the voltage to your RAM a step and see does that help. If you can't get it stable with a little more voltage, then you may need to downclock. Please think seriously as you pass 2 volts if your memory isn't rated for that - 1066 or better will be. Others? less likely.
I have my 4 running at 800, 5/5/5/15, @ 2 volts. But they're rated 1066/2.2v. My board would do the 4 to DDR2 1000 at 5/5/5/18 and 2.3 volts. But I wasn't comfortable running them that hard since I'm not a benchmarker and want the system to last a couple years. So I dropped it to DDR2 800 2v, and it's now happy to run like that 24/7. I don't have a temp reading for the DIMMS - They're warm to the touch, and cooler than my NB heatsink which I hae measured at around 44c (400Mhz FSB) So I'm happy with the result.
There is no real need for anymore then 2gb of RAM at the moment if you increase this to 4gb for example you won't see any more improvement because your system has nothing to do with it, it will literally catch dust