A few recommendations:
(1) If you can then start with a clean disk (no partitions at all) and do everything from OS/2. Set the disk to LBA mode (you will see the LBA addressable 8 GB of the HD, you will see more later, after installing a better HD driver).
(2) I am not sure whether PC DOS FDISK has made something wrong with your MBR. (I am speaking about the "non DOS" pratitions with wrong size.) In the end, PC DOS is not the same as MS DOS so that I cannot exclude it. I had the best experience with DOS 5 (MS DOS) FDISK. Delete all partitions with this FDISK. Ignore senseless partition sizes, the FDISK does not understand well big partitions but it is able to delete them flawelessly

(3) Another problem can be PnP. Disable PnP during installation.
(4) Next problem can be the CD ROM driver. Let us suppose you can read CD (from the installer).
(5) Start the installation, select "Advanced Installation" and you get OS/2 FDISK. Create a 2 GB partition at the start of the disk, make it bootable, save changes and quit. This will cause restart. Next time, you select your partition for installation.
(6) Install bare bones OS/2. Format the partition HPFS. Do not install anything you can install later. Install only standard drivers related to your machine and offered by the installer. Do not install network (this can be done later) and sound (this also can be done later). Do not install APM, PCMCIA, etc.
(7) Install HD driver. You need the files mentioned by ddan. Restart. Now, you should see the whole HD and you can create additional partitions.
(

If you have a video driver for your video card, then the driver is GRADD most likely. You will need to install FP5 at least for Warp 4 (you should install the fixpack at any rate to get rid of certain bugs in the plain system), you should not need fixpacks for Warp 4.5
(9) Now, it's time to install so far not installed parts of the system.
You should pass both with Warp 4 and Warp 4.5 Note that the diskette producing program on the Warp 4 CD is a DOS program. The program can be started directly from the CD. Therefore, you can put your CD into some machine, prepare 3 diskettes, open a DOS session, and run instcd (or cdinst - I don't know right now) from the root dir of your CD. Note that the machine must have a standard, ATAPI diskette drive, not a USB one or some extra drive, which needs a special driver.