Compaq dc5800 - Microtower PC Reference Manual page 218

Table E-5 Solving Media Card Reader Problems (continued)
After installing the media card reader and booting to Windows, the reader and the inserted cards are not recognized
by the computer.
Cause
The operating system needs time to recognize the device if the
reader was just installed into the computer and you are turning
the PC on for the first time.
After inserting a media card in the reader, the computer attempts to boot from the media card.
Cause
The inserted media card has boot capability.
210 Appendix E Troubleshooting Without Diagnostics
Solution
Wait a few seconds so that the operating system can recognize
the reader and the available ports, and then recognize
whatever media is inserted in the reader.
Solution
If you do not want to boot from the media card, remove it during
boot or do not select the option to boot from the inserted media
card during the boot process.