I would tread carefully here.
The first thing I would do at this point is backup your Windows installation. Create a full image that can recover the OS and your files and probably do a separate backup of your data only.
Second, I would attempt to make the install media from the hidden partition if you haven't already done so. There should be software included in your windows installation to do this. This usually creates a couple of DVDs so I don't know how it would work without a dvd burner, maybe it can make a usb recovery drive? If not, complain to the manufacturer!
If you still want to install linux on your hard drive you can use EasyBCD. I know WhoDo (Puppy 4.2 series developer) swore by this method. It involves altering the Windows bootloader configuration and chainloads grub, grub4dos or lilo.
http://en.wikipedia.org/wiki/EasyBCDLinux
EasyBCD can boot into Linux by one of two means:
Chainloading GRUB/GRUB2/LILO/etc.
NeoGrub
The traditional chainloading method creates an image of the GRUB/LILO bootsector on the local disk and loads this image during boot-time in order to chainload the second bootloader which should already be configured to boot into Linux or BSD.[12] EasyBCD has profiles for and officially supports the chainloading of GRUB (Legacy), GRUB2, LILO, eLILO, and Wubi (for Ubuntu).
EasyBCD also ships with NeoGrub, a customized build of Grub for Dos, which can be configured by editing C:\NST\menu.lst with the standard Legacy GRUB syntax for directly booting into the needed Linux or BSD partitions, or chainloading another bootloader to load the OS in question.
That's the best I can offer for the moment.