I reinstalled the original, unpatched BG1 (5-CD) and ToSC a couple of weeks ago onto an XP Pro machine, no issues other then the BG install doesn't 'see' all the space available on an HD using NTFS. If you want to install all the CDs, just choose 'continue anyway' when install says you don't have enough room (assuming of course you actually do have room
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Last week I installed the 3-CD package that includes all of BG1 AND ToSC as well as the official Bioware patches. Once again, no issues with XP AND this version 'sees' the actual space available.