For logicheskie virtual drives?

If You have Windows XP download Virtual PC, in its composition there is a utility which can be used to mounting VHD of the drives in the host system.

160Gb WD Caviar Blue WD1600AAJS SATA-II 7200rpm 8Mb — 1160.12 RUB
250Gb WD Caviar Blue WD2500AAJS SATA-II 7200rpm 8Mb — 1163.24 RUB
320Gb WD Caviar Blue WD3200AAJS SATA-II 7200rpm 8Mb — 1213.28 RUB
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I think you're not from that side approach to the issue.
In an extreme case, pererezat your drive into two (three, n) disks, but still that logical drives that the containers — the brakes have still to be since you will be storing both data and system on the same physical disk. The maximum that you will achieve — the lack of fragmentation of the primary partition, which of course is good, but not very helpful to you.

You can Google on keywords "virtual drive". From simple privaron that support not only CD/DVD but hard drive, immediately I remembered FileDisk and ImDisk (both open source), but I do remember that there were others.
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PS: I Assume we're talking about Windows, because in Linux mount-o loop.

In Windows 7 (maybe sooner) built-in virtual hard disks are.
If you want to use a large number of small files used them, it worked quite quickly and regularly.
"Computer management" — "disk Management" menu Action — Create VHD, Attach the virtual hard disk