I now have Fedora 15 dual-boot with Windows 7 on my HP Pavilion dm4t laptop. Here's what worked for me; which is Mariusz W's instructions with minor clarifications and a picture.
The idea is to remove a primary partition, HP_TOOLS, and place the contents into an extended partition with the same name. The laptop's BIOS, which uses these tools, won't know the difference - but Fedora can now be installed.
The partitions were configured as: C: (Windows), D: (Recovery), E: (HP_TOOLS). I forgot to grab a screenshot before I made changes.
1. Start the Disk Manager utility by typing "manage" in the task bar and selecting "Computer Management." Go to Storage --> Disk Management. Note the size of the HP_TOOLS partition, 103 MB.
2. Insert a USB stick and format it as FAT32 from within Disk Management. Right click on the partition, New Simple Volume... Hit Next 3 times, format as FAT32. (existing data erased).
3. Use the built-in Windows 7 copy utility, robocopy, to copy the data to the USB drive. This saves everything for later.
Code:
robocopy E:\ G:\HP_TOOLS\ /E /DCOPY:T /XA:S
4. Delete the HP_TOOLS partition. Right-click, Delete Volume... The space will show as unallocated.
5. Create room for Linux by shrinking the Windows 7 (C: ) partition. Right-click Shrink Volume..., accept the smallest amount it will let you. You now have an extended partition as free space, where Fedora will be installed. On a 500 GB drive, it's much more than you'll need.
6. Inside the free space, create the extended partition for HP_TOOLS. Right-click New Simple Volume... Use the same size as the original partition, 103 MB, assign a drive letter "E" (needed for next step), format the volume as FAT32, volume label "HP_TOOLS" (note the underscore between HP and tools).
7. Copy the USB stick HP_TOOLS files into this new volume.
Code:
robocopy G:\HP_TOOLS\ E:\ /E /DCOPY:T
8. Reboot and check that Windows 7 is OK. For this first time only, Windows 7 will complain that it was not shutdown correctly. Proceed without repair. Start Computer Management and check your work. HP's diagnostics are functioning.
A screenshot of the partitioned result, the Fedora install DVD and USB stick are loaded: 
9. Boot the install DVD. Select the basic video driver or you may get a black screen. Install with the Use Free Space option. Hint: When presented with the boot options, change "Other" to "Windows 7" and select if you want Fedora or Windows 7 to be the default OS boot.
I did additional research to be sure that Microsoft's "Simple Volume" is indeed an extended partition. It's shown clearly after-the-fact in the screenshot. HP_TOOLS and Free Space have a dark-green "extended partition" box around them.