SUCCESS!
As it was before I screwed it up by deleting the QP partition without researching it first, I now have a 1027.6MB partition of Type D7 (according to an old version of Partition Magic Pro), and am able to boot directly into QuickPlay Direct 2.3.
I'll condense the instructions into one post, as things stand now (eventually we'll hopefully get the full package hosted but for now it can be pieced together). These are for a reinstall of QP Direct without bothering your other partition/s (except maybe resizing if necessary):
1. Back up your system in case of catastrophic failure (always a good first step when jacking around with partitions).
2. Download HPQPDP.rar or HPQPDP.zip, from
http://ridickulous.net/quickplay/
3. Extract whichever you downloaded and drop the resulting HPQPDP folder into your <boot drive>:\SwSetup\ folder (mostly for safekeeping purposes).
4. Using PartitionMagic Pro or Disk Management in Windows something else to either shrink your main partition, secondary partition, or whatever. You want to end up with a 1027.6 MB (or 1028 MB) UNALLOCATED area of space at the END of the drive. Go through all the reboots the machine will likely want to make this happen. It can't hurt to verify that the unallocated space is there and unallocated after all this. (NOTE: If Partition Magic keeps giving errors saying "Selected disk contains one or more Partitions which cannot be moved," you have a recovery partition that prevents it from doing what you need it to or drive information has changed. You may have to find another way of resizing your partitions or a reboot might solve the problem.)
5. After creating the unallocated space, assign it the drive letter X: but DO NOT FORMAT IT.
6. Hie thee to the HPQPDP folder and run setup.exe.
7. Wait.
8. Wait some more.
9. Reboot and keep on waiting.
10. Shut down the laptop and hit the Quickplay button. You WILL most likely see a Windows logo, since QP2.3 is Windows-based whereas QP1.x is Linux-based.
11. Enjoy a celebratory glass of single-malt scotch, and pop in or browse to your favorite flick. This step is optional if you are at work and/or not legal drinking age.
MANY thanks to everyone for their input. For the above files, thanks to modemboy for providing the .rars and to AmigaDude for the valid data2.cab and data3.cab files. Also, thanks to Ericko for the QPv1 image (found at
http://www.megaupload.com/es/?d=QVE3S9PU) in case someone's machine cannot run QP 2.x, and to everyone else that pitched in.
[Disclaimer: the 1.x image may not work in all machines. It looks like it was taken from a disc that shipped with a dv4000 CTO; YMMV. See the following article if you need 1.x:
http://h10025.www1.hp.com/ewfrf/wc/g...reg_R1002_USEN
If you need QP 1.x and you created your recovery discs you have another option for restoring QP; it is listed in this article.]
This message was typed in anticipation while QP was installing.
[Edit: linusl also provides a more complex way of getting QP2.x to work under different circumstances if your QP partition is still intact - see page 42 of this thread.]
[Edit number 2: Changed slightly since files have ben re-uploaded.]
I try to help whenever I can.
OMG 
