XPPro on a IDE drive + 1tb connected at power up = no boot (it hangs on the black windows logo screen... actually if you leave it long enough (=10 minutes or so) it does boot but the 1tb disc is not present (eg in Administrative Tools -> Disk Administrator).
Same OS + 500Mb sata boots fine
Same OS + same 1tb disk connected after boot works fine
XP Home on same machine with 1Tb disk boots fine (admittedly I had to do some partition recovery since it booted on this OS and I no longer have the OS).
Any suggestions? Google reveals some stuff about LBA and the like.