There is no way a disk wipe should take 2200 hours unless the drive is failing and cannot be written to. I would run the Dell diagnostics by tapping F12 at boot.
Modern drives can be securely wiped with 3 passes and 7 is overkill. In fact on a modern drive one pass is sufficient unless your trying to hide something from a government.
You can use a bootable disk of Partition Wizard to zero wipe the disk for three passes.
When you say the drive is locked can you explain. Has the drive been encrypted? Usually a hard drive password is used only on laptops. There are BIOS passwords on a Desktop but those can easily be cleared using a jumper on the motherboard.
This is a very old system and I would not spend any money on upgrades other than increasing your amount of RAM. Last BIOS update on the computer was Oct 2002. If the computer is operating normally I would not flash the BIOS.
What did you plan on using the computer for? Were you planning on sticking with XP as an OS. It is no longer supported and no longer has security updates.
Depending on your budget see this page. It may help you decide on what to upgrade. The problem is this article was written in 2010 and the video card is no longer available new unless you pay an unrealistic price. You may find one used. Also you should have at least 1GB or RAM and preferably 2GB. Note the page says to use 45ns RAM which is wrong. Your specs say 40ns and all sticks need to be the same speed. If you do plan on replacing the CPU remember to clean the thermal paste off the Heatsink fan and replace with new paste. I don't know how much computer experience you have. Just pointing out things to watch out for.
Here is your maintenance manual showing your specs. Maximum Memory is 2GB and the maximum memory stick size is 512MB of RDRAM.