"Is it just a matter of using Acronis to copy everything from the IDE HDD to the Sata HDD? "
Clone the drive, not copy
"I set it as master and just swop over HDD's"
SATA does not have MASTER and slave you ned to connect to the lowest SATA port number on the board then reset the BIOS to boot from the SATA drive before the IDE drive.
"Is there any problems with Win XP being put on another HDD, or is there only a problem when the same copy of XP is used with a different MB"
No problem you need to change 4 pieces of equipement before needing to reactivate windows.
"Do I have to do any thing to the Bios on startup?"
Yes reset first boot device as SATA hard drives.
"Will the Sata HDD work ok with the slave IDE HDD?"