Bad clusters

Scandisk will identify and mark bad clusters so they won't be used. It's fairly accurate altho it misses things or includes non-bad clusters, sometimes. Format will attempt the same. If you have a bunch of bad clusters and more keep showing up it's probably a good time to get thtat new hard drive you've been wanting. This can be a sign that the old grey hard drive ain't what she used to be and will likely start losing data; then more; then all of your data.
Utilities like Norton (Symantec) have excellent programs to identify bad clusters, but nothing will repair them if they are really bad.
Try reassigning your com port rather than deleting it. Since you didn't say what computer/operating system you have I can't be more help

If you have many bad clusters on you drive it might be a good Idea to try to recover them with a low(mid)level format. Most
bran name drives have these utilities such as Maxtor has MUD, seagate has diskwizard ,Whats the bran name of your drive
go to there home page they should carry some util for this.
BUT by doing this you will lose all data on the drive so if you
go with this option BACK UP YOU IMPORTANT DATA BEFORE YOU DO THIS.if you can't find it let me know I'll send it to you.
good luck.hope this helps.

Gward28: I'm not aware of any utility that will repair bad clusters since these are physical problems with the HDD surface. How do they work?
I know that, sometimes, the data in a bad cluster can be recovered but this is a "cross your fingers and pray" situation. The few times I have had to try this I went through a professional data recovery service and got about 15% of the data in a useable form.
The format routines I'm familiar with just mark the bad clusters so they can't be used.