As always, the bigger and faster your PC, the better. RD-D will run on almost any machine. The only question involved is how fast it runs. The main test is the rubber tool itself. Try using the eraser of maximum size. Does the square plotting of pixels accompany your movements of the mouse easily, or is there a great lag between the new position of the mouse and the pixels currently being plotted? Of course, you can always use a smaller eraser or move the mouse more slowly in order to alleviate the problem, but beyond a certain point this becomes inconvenient. I suggest that a minimum machine for use with RD-D is the one I am using at the moment: a Pentium II of 450 mHz, but with a decent mother-board, 128 MB of memory, and a common video board.*
Please note that Rubber Dub-Dub requires a video display with a colour depth of at least 24 bit 16.7 million colours. If your video board does not support such a display, or if Windows is set to use an inferior display, RD-D will not run. Try to use a display size which is larger than the picture you intend to work on. You cannot work on a picture which is larger (in pixels) than the size of the screen.
Apart from the machine itself, the only other consideration is the Windows platform. RD-D runs more or less equally under Windows 98, ME or XP. RD-D is NOT supported by Windows NT or Windows 2000.
* If you would like to eke out a little more performance out of your PC, you might give Moonlight's "Priority" a try. In their own words:
"Speed up your programs with this simple utility. Priority runs in the taskbar, monitoring programs as they are started. Once a new program is started, Priority changes the CPU priority of that program to high. Your programs now run a little faster and smoother."
In my own case, in relation to Rubber Dub-Dub, I found that the use of this little utility program was indeed significant. The software is free, and if you click on the Moonlight banner below you will be taken to their download site.