An 80Gb and 40Gb hdd's are not a lot of space to do what you propose. the OS partition for XP should be no less than 30Gb alone, since updates and many software titles prefer to be loaded on the OS partition. You could split the 80Gb hdd in two at best imho. Backups take up a lot of space, especially if you intend to save music, pics, videos etc the page file will most likely consume 1.5-2Gb of hdd space by itself (typicall page file is 1.5 X total memory) You'll not have a lot of space left to do much in a very short time. If you can I'd go for a much larger hdd (500Gb) use the 40Gb drive for the OS, the 80Gb for back ups and page file and the 500Gb for storage.....
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