I am posting this in case someone else has similar experiences. On a recently purchased Dell Inspiron 1721 with 2GB RAM, 2.20GHz Turion 64 x2 AMD proccessor, and ATI X1270 display adaptor running Vista Ultimate, every time I try and install Windows XP, Windows 98se, or Fedora Core 7 the Parallels VM freezes and often brings Vista to BSOD. Other times the attempt of installing an OS results in a spontaneous re-boot. I don't think this is a Parallels probelm however, since I don't see anyone else having these problems and I've been able to install Ubuntu 7.04. Strange . . .
More information on Inspiron I find this in the event logs after each crash . . . "The Parallel port driver service failed to start due to the following error: The service cannot be started, either because it is disabled or because it has no enabled devices associated with it." This error comes up even after I uninstall Parallels and try installing guest operating systems on Microsoft Virtual PC 2007, which also fails in re-boots or freezing of system.