Suspected Virus - can't boot in windows xp professional

Several days ago my Dell XPS 410 with winXP pro had some popups for 'virus protection' to remove malicious items from the PC. I tried to 'x' out of it, but I think it was too late. Mcafee picked it up as a trojan I believe, but it happened fairly quickly and I don't recall the name. Mcafee tried to delete it, but it kept coming back, with a red x icon in the sys tray. Eventually, task mgr and even system restore would not work. Even when I tried to boot in the safe mode, the icon was there and there were pop ups to download a removal tool and clean things off. Now, can't even boot up - safe mode or not. The PC looks like it tries to logon when a user is selected, then it just goes to saving files and logs off. Since I can't boot up, I cannot provide a HJT log. I am using another PC now to be able to post this question.

Thanks, any help will be appreciated.

Hello.
Do you have your XP disc?

Hi Belahzur. Yes, I have my Windows XP Pro disc.

Hello.
Okay, put your XP disc in and reboot the machine.

Lets try and perform a repair install, read here how to do a repair install.
http://michaelstevenstech.com/XPrepairinstall.htm

Thanks, I'll give it a shot. I'll report back what happens.

By the way, if there is a virus on the hard drive, as I suspect, do I do something after the winXP repair - if it works - to get rid of the virus? It seems my Mcafee did not do the trick the other day,

Yes, we'll get rid of the malware once we can get the machine to at least login.

Well, so far it did not work. Everything looked like it was going well, but one file did not load - I passed by it. All else went well and the install completed. When it went to the reboot after configuration, it will not go into windows. It tries for a second, then a BSOD flashes for micro-second and it goes into the windows did not load properly window and asks for a selection - safe mode, safe mode w/networking, etc. I tried all to no avail. The BSOD flashes briefly and it goes back to the Dell window. I'm trying once more to do a winxp repair - i'll note the file name if it fails again.

Hello.

Lets try using the Avira boot disc.

Avira AntiVir Rescue System is a Linux-based application that allows accessing computers that cannot be booted anymore.

• Download The Avira AntiVir Rescue System from Antivir.de.
  
• Just double-click on the rescue system package to burn it to a CD/DVD.
  
• Then please use that CD/DVD with Avira Rescue System to boot your computer.
  

You'll get a boot option to either boot from hard drive or AntiVir Rescue System.


Press the number 2 on your keyboard to boot into AntiVir Rescue System.

Please wait until drivers are loaded and Main menu shows. Then please select the second option “Scan your system with AntiVir” and hit Enter.


Under Configuration, please select Scan all files, Try to repair infected files and Rename files if they cannot be removed?.


Then please start the scan.

The Avira AntiVir Rescue System wil now

• repair a damaged system,
  
• rescue data,
  
• scan the system for virus infections.
  

UPDATE - I tried the install again and it found the same file missing -"IaStor.sys". I found it in the drivers folder and the install is continuing.
When I have another update, I'll let you know. If you read this before then and i'm doing something wrong, let me know. Thanks!

Sorry - it looks like I was posting at the same time as you! It's in the middle of the XP install. As soon as it's done, i'll have the CD ready and try the Avira rescue CD.

Thanks for that, stop everything, that's why your machine can't boot, iastor.sys is a needed system file.

editing this post in a sec

Okay, let the install carry on till it's finished, then try booting normally. If not, we may need to replace iastor.sys, sounds like the malware tried to destroy your OS there.

Thanks. It's just finishing up. I'll let it go through with the install and reboot. I'll let you know what happens from there.

Ok - it's finished and it actually let me boot up! I have not yet seen any of the pop ups from before either. It is not online yet - i have disconnected it from the ethernet.