If you still get an error about autoexec.nt, that is not going to fix itself. Again, this "problem" is an "effect", not a "cause". But you can fix the autoexec.nt and also likely config.nt by actually creating these files in your system32 folder.
Create a new file called "autoexec.nt" in the system32 folder. Put this in it and save it:
@echo off
lh %SystemRoot%\system32\mscdexnt.exe
lh %SystemRoot%\system32\redir
lh %SystemRoot%\system32\dosx
Once that is done, create another file and call it "config.nt" and put this in it:
dos=high, umb
device=%SystemRoot%\system32\himem.sys
files=40
Then save.
If these files already exist, just check them to make sure they only say something to this effect.
Also note that it is your virus problem that is likely killing these *.NT files. So you may have to create them again if you restart.
Once those files are created, try your regedit again. You shouldn't have to do anything except click start-run and type "regedit" and go.
Also guys, it doesn't matter AT ALL if regedit has an EXE extension or a COM extension, as long as it's the real, non-infected file. I know this because I get PCs sometimes with EXE file associations messed up. I just rename regedit.exe to regedit.com and it opens fine so I can fix the EXE association. Then rename it back again.
Izopyn, please just stay in Safe Mode with Networking (assuming XP). If you restart before it's clean, you WILL be reinfected upon startup until those startups, AND files, are gone for good.
Please run the autoruns program and tell us what is in the various tabs. I suspect you have a WininitDLLs or Notify entry that is reinfecting you with winupdates. Possibly a service as well. Which autoruns also lists.
We may have to employ more tools then just HJT, as the virus obviously puts itself back in immediately after killing the entries.
One thing I will say is that the virus, or whatever it is, is likely attached to explorer itself. To check that theory, while in safe mode, open up task manager (ctrl-alt-del) and CLOSE "explorer" and anything that says "explorer" in the name. This will make your icons and start bar and all, disappear.
Now, with task manager still open, close your "bad" processes. Right-click the name and select "end process tree".
Once your bad entries are gone, and they are NOT spawning back in. Click "File-new task" and browse to your Hijackthis program and open it. Do a scan and remove all the sticky ones again. Scan again and make sure they stay gone.
Then do new task again and run the "autoruns" program I told you about. Remove the bad service or whatever is causing this. Possibly in the "Notify" registry key. Once those startups are removed, and STAY removed, click new task again and run "explorer". This will bring back your icons and start bar.
Continue to watch the task manager and make sure your bad processes don't come back. Watch HJT and make sure those don't come back.
Next search for any noted "bad" files and delete the files. Go into your System32 folder. Click View-details. Then click to sort by date. Look for any files that were created TODAY, as in, the day your are looking. If they look funky, delete them. There really shouldn't be any brand new files in this folder (except autoexec.nt and config.nt that you made earlier).
Now that the startups are gone, the HJT entries are gone, and the files are gone; you may want to run a better registry cleaner. I suggest downloading RegSupreme 1.3 from
http://www.macecraft.com/downloads/
Install that and open it. Click OK to optimize the registry. Then do a Normal scan. Clean all it finds.
The purpose of this scan is that, if the files on your hard drive are deleted, ANY entries in the registry that still point to them will be found and removed because the file is missing. Doing a registry scan like this will remove entries of missing files. That's the most important. If you like, once it finishes scanning, look through the "Problem" column and anything that says such and such file is missing. Look at those file names, you may see your bad files in there.
So clean all it finds.
Once you've ran all this stuff, check them all AGAIN, to make sure it's still gone. If the bad process starts up again, you may have to start over. It is important to do everything in the right order. The processes MUST be closed before removing startups or the entries will be put back in. You MUST delete files before cleaning the registry or the entries in the registry will still be there. Etc...
I hope this isn't information overload, but this is going in circles, you remove it, it comes right back, time for some higher-caliber guns.
Hope you can get rid of it!