As cheap as RAM has become, 2GB should really be your starting point. Go with 4GB if you can afford it.
For example, Adobe Creative Suite 2 Premium apps ran okay on my notebook with 1GB of RAM. When I maxed it out at 2GB of 533MHz DDR2 SDRAM there was a big speed improvement, especially with PhotoshopCS2.
I think Dell PCs are fine. We have a bunch of them in our shop and all have been very reliable. However, I will add we don't go cheap on the units we buy. In doing that, any given computer in our studio can last several years. I'm typing this post from a Dimension 9100 (equipped with a Pentium D 840 CPU, 2GB of RAM, 250GB SATA hard disc, 256MB GeForce6800 video card, Audigy2 audio card with IEEE port, DVD+/-RW burner, etc.).
We are in the process of replacing a old 1999 P3 550 Dell tower with a new computer we're building ourselves (as an experient to see how well the process works). Had one snag immediately. Newegg sent us the wrong Asus model motherboard. This new machine has better equipment than the one I'm using (Pentium D 920 CPU, 2GB of Corsair DDR2 RAM, 400GB SATA HDD, 256MB GeForce 7800GT video card, dual layer DVD burner with LightScribe capability and a number of extras such as front side Firewire and USB ports).
As to the "get a Mac thing," it's a funny joke. But pretty difficult to manage in reality. Once you have been working on either platform for any given amount of time you get locked into it quick. The price is HIGH for jumping to a different platform, even going the Mac to PC route.
I was disappointed to hear Microsoft will not feature support for Intel's Extensible Firmwire Interface (EFI) in the upcoming releases of Windows Vista. EFI is a 64-bit "bootstrap" that replaces standard BIOS chips. You'll find EFI instead of a BIOS chip in any new Intel-based Mac. The lack of BIOS will prevent any version of Windows from running natively on a new Intel based Mac. Until Windows Vista adds support for EFI, that incompatibility will remain. Unfortunately that will also kill any intentions on my part of buying a Mac. I'm not going to buy one unless I can dual boot a copy of Windows and run my existing applications on it. The cost is simply too high to have to buy everything all over again.