Yep the paging file, (I deal with Unix all day at work so deal with swap space there so tend to always use that term), you can relocate WinXP paging files easily enough using the System applet in Control Panel, (System -> Advanced Tab -> Settings (Peformance) -> Advanced Tab -> Change (Virtual Memory)
But I would not move it to the D: drive ... the D: drive is a much slower SSD so you don't want to page to there. You really want paging turned off completely on the EEE's (I am pretty sure that the preloaded XP comes that way too) as the number of writes having it on will generate may affect the life of the SSDs. Given memory prices it's easy enough to drop 2GB into a 901 if you are worried about memory capacity (first thing I did with mine) and XP runs great with that even with paging off.
Ok, I managed to turn off the page file and trim a little from XP and I got SP3 to install but now I only have 20MB of space on drive C: The problem is that I want to install Acronis True Image once it's all setup and take an image for quick repairs later on. Acronis needs extra disc space on C: to install though, even though I'm actually installing it to D:...!!!!!