As an example, I'll just throw out my laptop's basic specs:
Core 2 Duo T9300 @ 2.5 GHz
4 GB RAM
GeForce 8600M GT
7200RPM HDD
I'm able to pretty much record anything Touhou-related without problems. A few hitches tend to occur though, especially when the 4GB max is reached for each individual .avi (at this point, FRAPS makes another humongous file). To get past this issue, I usually make 2 or more recordings of the same replay, starting at different times. I then splice them together to get a single video that runs perfectly fine from beginning to end. The laptop is a year old now though, so obviously you should try to aim for something better (especially if you're getting a desktop, at which point, getting something way better won't be expensive at all). You'll probably run into no recording issues whatsoever with a better setup, aside for the possibility of a quick bump when the aforementioned 4GB max is reached.