Had all sorts of problems having 32 bit XPpro/SP2 on master drive and 64 bit version on scondary drive. Both installed OK but when re-booting both drives in the boot procedure annound that the were the default drive and neither would open normally with an error notification "ntdlr corrupted" Could open the 32 bit in Safe mode but could not modify boot.ini
My system works OK with 32 bit on both drives.
Note: they are physically separate drives.
Anyone know how to sort this out, please?