You haven't told us anything about what you're rendering. What resolution? What codecs? Is it a complex project? What is the resolution of your source footage and graphics? Are you using multiprocesssing? Are you using OpenGL to preview?
One thing for certain is that 4GB of RAM is at the minimum end of specificied requirements, and that will certainly slow things down, especially if you're working at high resolutions.
First, welcome to AE.
Most people here think of using the software as journey, and not something that can be totally mastered. That's an important differentiation from most applications, no?
Another important differentiation: knowing the basics is the key to doing the impressive-looking stuff in AE. There is a formidable number of little details to learn at the beginning which will relieve dead ends and frustration later. If you start at the beginning, you actually progress faster later on. Here's a good starting point:
Don't overlook the links within; they're valuable. Other good learning resources can be found at videocopilot.net (free), plus Total Training ($$$).
To answer your question directly, I'd say yes: it IS reasonable to ask for something better. AE is a RAM hog, and in AE-Land, 4 gigs is almost nothing. If you must have a laptop, make sure it's filled up with memory. Serious AE power users would advise forsaking laptops altogether and going with a desktop machine.
To ease your task in the interim, I would do a few things:
Got multiprocessing (aka Render Multiple Frames Simultaneously) turned on? Turn it off and keep it off.
Got Open GL turned on to accelerate rendering? Turn it off and leave it off.
Got any footage in a project from a consumer camera, XDCam, HDV cam, helmet-cam or DSLR? Use a different application than AE to convert them into LOSSLESS footage. The files will be huge; that's life in AE-Land.
Dave and Andrew are right (of course). Here's an FAQ entry that can help you to determine what kind of computer is most suited for After Effects:
Thanks for the reply, all I am rendering at the moment is a few samples that i am playing around with entering my own text. Just keeping to the default settings, I am rendering as video for windows 640x424, no compression
It's the underlying video source we need to know something about as well as your basic knowledge of video formats and codecs. Most beginners fail to realize their base video is highly compressed, like, say, H.264, and must be unpacked frame by frame for every operation or movement of the playhead. There are so many weird factors that can impact AE's processing. When you activate any 3D functions, your processing time can increase by a factor of three or even nine!.
It really doesn't matter how much money or speed or RAM you throw at it, you will always want more.. You learn to edit in AE using the tools and settings that allow you to work the fastest while previewing and then you learn how to prerender, preprocess and precompose to speed your workflow up. These are advanced concpets requiring planning and experience. You'll get it but it takes time.
Performance speed for After Effects is relative. My first AE machine took a weekend to render ten seconds of video, one effect on one layer. Welcome to the family.
Sorry, I know nothing about PCs (and I like it that way) but you will get excellent advice form others in a bit. If you do not, you can always try a new thread, "Recommended portable?" but you really should try searching first or just find the minimum specs on the CS5.5 pages and throw money at them. You just keep adding resources for After Effects and it will suck up whatever you can afford and keep asking for more.
I'm a Macintosh user. Many of my contemporaries do well with the top end MacBook Pro but they're not using it as a laptop, it's just a box. They hook it up to a second, much larger monitor, use a mouse or tablet and a bunch of external drives.
The crucial question when using a laptop for AE work is, "Do I mind if AE runs slower than it could on a different machine?"
Sure, you can use one, but because AE relies on fast processors and a boatload of memory for speed, the best you can do is to stuff fast processors into your laptop, then trick that baby out with RAM. It won't have as much memory as a desktop, so you'll probably never be able to match a desktop's speed.
If you can live with that, go for it. And max out the memory.
Laptops can be fine for basic design work, as long as you are realistic in your expectations. The ideal situation is to have a beast of a desktop workstation for serious work and rendering, and have a laptop for mobile work. If you try to make the laptop capable of the serious work and rendering, you'll throw a _lot_ of money at the problem---and still not get there. Keep in mind that laptop components are far more expensive than equivalent desktop components. You can get an extraordinarily powerful desktop computer for the same price as a moderately powerful (or even puny) laptop.