If the CD drive light starts flashing before Windows starts to load, your problem is most likely hardware and not related to the new printer.
First, verify that the drive itself did not just happen to fail at the time you installed the new printer.
Unplug the IDE cable from the drive and see if the symptom goes away.
If the light still flashes, the drive is not passing it's internal POST test and will need to be replaced.
If the light stops flashing, and you can play an audio CD using the front panel buttons and headphones, chances are the drive is good.
Try a new IDE cable and see if the drive now works.
If the light starts flashing again after connecting the IDE cable, you may have a bad IDE controller.
You can also try unplugging the USB cable for the printer to verify that the USB and IDE controllers are not in conflict.
"IF" the drive light starts flashing after Windows starts loading, the HP Printer driver likely updated the USB driver for your motherboard. In doing so, it may have damaged the driver for the IDE controller.
CAUTION: Chip-Set driver installations can break other drivers.
Be prepared to re-install any system device driver.
I recommend that you install the latest W98 version chip-set driver for the specific chip-set on your motherboard.
Either download the latest version from Dell, or (assuming an Intel based motherboard) download the proper archived chip-set INF utility from Intel.
Chas