Severe problem, need help

Hi everyone, i've just finished the end of a long day trying to fix my partners pc, the problems in no particular order are:

1. Unable to install updates (i can download)
2. I can start a virus scan (using microsofts essentials) but cannot finish it
3. I cannot enter internet options from control panel or IE8' toolbar
4. Almost all attempts to resolve this seem to be blocked either by preventing a download into a folder or the resetting of software
5. Anti-virus software resets to pre update state at random times and constantly reverts to 'at risk'

the pc is running
WIN XP HE
IE8
Service Pack 3 is listed in add/remove programs
2.6ghz single

I have tried about 18 different types of repair including:

1. Using start > run and addresses to bypass internet options - I had success with one and got in but as soon as i changed anything it just changed itself back, there was nothing that would indicate this problem.
2. I trawled through the internet logs for all updates and checked error codes, downloading various tools and fixit's from MS in the process
3. Tried various scans without success
4. Went through many forums looking at the older posts which appear to have had the same problem
5. Searched through the registry for the NOWINDOWSOPTION, (does not appear to be in my system)
6. Used a temp cleaner to clean out all windows temp files
7. Lastly i have left ad aware running overnight to see if that finds an error

I really do not know what else to try i am stumped :confused i am unable to buy any software as i just don't have any money so must rely on freeware, does anyone have any idea how i can resolve this, i only have 4 out of the 5 recovery discs so i cannot even re install, it's so bloody annoying, my partners panicking cause i'm getting so stressed as i've just had heart surgery, anyway gonna let blood pressure return to normal and hope theres some news tomorrow or at least a result with ad aware (it claims its free)

 

Greetings, photomorph, and welcome to MajorGeeks.

I strongly suggest you go through the Malware Forum's Read & Run Me First thread, perform all of the suggested steps, and attach the requested logs to a new thread in that forum.