Chromium OS on an EEPROM
HP's QuickWeb implementation of SpalshTop does not reside in flash, it uses files that are located on the Windows partition:
EDIT: Middle of page 3 on the HP pdf explains that there is a 2gb partition used in some cases: http://h10032.www1.hp.com/ctg/Manual/c01951773.pdf
http://phoronix.com/forums/showthread.php?28583-Hacking-HP-QuickWeb-(SplashTop)
EDIT: It's possible to dual-boot Chromium OS and Windows: http://chromeos.hexxeh.net/wiki/doku.php?id=multiboot