The 300 gb drive will not be relevant ’till you complete the wipe and reload on the new system.
If the 300 gig drive already had usable data and has been visable from another system the there are two possibilities.
It is an internal hard drive (ide or sata) in which case you should have no issue. You can connect it before or after the windows load.
If it is an external drive and will connect by usb or firewire, this could be the issue you had previously. If so let me know. Otherwise that is not relevant.
If the drive is internal and windows want to format it despite data being on the drive, I would have concerns about the condition of the drive and replace sooner rather than later.
James Lee is a systems administrator with backupanytime.
I just did the same thing, and have done it many times in the past – what I do is disconnect all extra hard drives so there is no possibility of touching those drives during the partitioning/formatting process. After XP install is complete and updated, then I re-attach the extra drives. Never had a problem with this method.