Go to Dell's site, put in the service tag for your system on their support site, and in the list of drivers you can download, there should be the option to download a diagnostic program. It's fairly small, can fit on a CD or USB flash drive. Do that and run it. I'm betting you'll find your HDD fails testing.
Since I'm guessing it's well out of warranty, you'll need to find out if it's IDE or SATA (probably SATA, but definitely double check), then buy a replacement. Unfortunately for you, there's something of a shortage of HDDs right now, and a lot of places have taken to gouging people. So, it's either pay a bit more than you should have to vs having a system that doesn't work.
In the unlikely event the drive passes testing, then you can come back here with that info, and we can go from there.
My computer has been running very slow lately, takes about 10-15 minutes after the computer starts up for me to be able to do anything. Constantly freezes when I'm using MS Office or the internet. I went on the Dell website and did all of the things they suggested for improving performance. One of those was to run CHKDSK when the computer starts up. I did this and it starting this morning, which was exactly 12 hours ago now. For about 6 hours now my computer has been stuck on 96%!!!!! It hasn't even changed the number of files processed in 6 hours. Should I try turning it off and rebooting my computer or will that mess something up? I have no idea if this is normal for chkdsk or if it is actually frozen.

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