That account is part of the .NET Framework. It's harmless, but if it bothers you, you can disable or delete it.
The spam could be from a lot of things, including the fact that lately spammers have stepped up their efforts in a big way. Though using Internet Explorer and/or Outlook/Outlook Express will not help matters at all.
You may wish to run a malware scan or two, using several different programs. Once you've cleared out all the malware, consider dumping Internet Explorer and Outlook/Outlook Express. Replace IE with either Firefox or Opera, whichever you like best. Email can be done by Thunderbird, or a myriad of other email programs, pretty much any one of which will be more secure.
Depending on how far things have progressed, it may just be faster and easier to format the computer and start fresh. If you do that, be sure you have a firewall running (either XP's or a third party one such as ZoneAlarm, or a DSL router with a firewall) before you ever connect to the Internet. Without all the security updates for Windows and IE installed, you can be compromised in minutes, and have to start all over again.
If you format, the first priority upon getting online should be to hit the Windows Update site, and install all security updates. The next order of business should be installing Firefox or Opera and never using IE again, unless it's to go to the Windows Update site to download new security patches. Never use Outlook or Outlook Express, just install Thunderbird or one of the others from the start. And if you install MS Office, make sure you download and install the security updates for it as well. You can either use Office Update or Microsoft Update, both of which can be found from the Windows Update site.
If you do that, and avoid file sharing programs and opening strange email attachments, you should be able to lead a rather problem free life in regards to your computer.
I think this will be my first thread on this forum and very little experience with any forum. I have windows xp home edition sp2 and internet explorer 7. I use internet a lot and have had dsl for over four years. I have fairly fast PC with lots of memory. I am getting spammed more than ever and hopeing not to have to change my email address which I've had about 10 yrs. I have norton system works 2005 with norton antivirus premier. I am now the only user on the machine and on the last changes in updating etc just left myself as computer administrator but without password since there are no other users. recently the log-in page has started appearing at start-up and after sleep mode periods. I have been very busy in my work so even though I have no password I have not done anything about it yet. I believe hackers are getting in the computer and phishng etc. Today when I went to one of my news web sites the opening window for my office suite application flashed across the screen. There have been many wierd things like that happen not to mention all the evidence of identity theft which convince me hackers are getting inside my machine. Today I opened user accounts in control panel to see if things looked normal and found a user account called ASP.net Machine A along with my administrator account. I don't know how long it has been there, If that is a normal part of recent upgrade to version 7 of browser, or if just some method of hacker phishing in the machine. I searhed the words on google and found nothing bad about it and that it is used by microsoft developers. I wonder though if some hacker might be using that as user acct or if it is there for some good purpose. Just today I activated windows firewall and hope that will help some.
I'm sorry to have such a long question but hope someone has some previous experience and ideas with this issue.