Since I have a number of Dell ESX 3.5 hosts managed by a dedicated Virtual Center server each Dell ESX host needed firmware updates. Here are the steps I took to update the servers without using a floppy drive:

1. Go to the Dell support site at http://support.dell.com and go to the drivers and downloads section for your server. Choose Red Hat Linux 4 as the OS type.
2. In this case we’ll update the system bios, so expand the Bios section and download the Update Package for Red Hat Linux which should be a .BIN file (like PE2950_BIOS_LX_2.3.1_1.BIN) to your local machine.
3. Next, download and install WinSCP (http://www.winscp.net) on your local machine.
4. Open WinSCP on your local machine and enter the ESX server IP or hostname, username of root (or, if you were smart, a user you configured with less privileges), and the user’s password.
5. Once you’ve logged into ESX, switch to the /tmp directory and create a directory called “dell” (or whatever you want).
6. Upload the .BIN file to the dell folder on the ESX host.
7. Migrate all the VM’s off the host you’re about to update and place the ESX host into maintenance mode as a reboot will be required after the following update.
8. Now, log into the ESX server console using Putty (http://www.chiark.greenend.org.uk/~sgtatham/putty/) and switch to the root user (if you logged in under a different account) by typing “su -” and entering the root password.
9. Switch to the dell directory you created above by typing “/tmp/”.
10. Type “ls” or "ls -a" and make sure your .BIN file is in the /tmp/ directory.
11. Give the .BIN file execute privileges by typing “chmod +x filename.BIN” where filename.BIN is the exact (case sensitive) file that you uploaded.
12. Now execute the update by typing “./filename.BIN”. This will start a Dell dialog that you should read. When you’re done reading type “q” and it should execute the update.

You can run this same procedure for any other firmware updates you need to do. See, short and painless.