Windows Vista Problem with Vista

Hello Friends

My friend has a dell inspiron 1525 laptop with windows vista premium sp1. It worked nicely for 5-6 months and now suddenly its giving a problem

The problem is

All files got converted in to .exe files and when i try to open them they show only options of open with and even internet explorer also giving the same problem when i try to open it by double clicking the ie window opens first and then suddenly it shows the message do you want to run or save this application like the msg something which we get when we try to download so when i pressed to run, it again opened in open with options box and when i press open with ie it again repeats the same issue and we are not able to open any file or run any file not even system restore. we have tried system restore in safe mode but bad luck there was only one restore point that also on the day of the problem and also i tried to install an antivirus but disnot install.

I have tried to solve by downloading some .exe fixes
I tried to format the drive with vista but it shows an error msg
I tried to downgrade the os to xp using the procedure given in Microsoft Vista website[/B]

The thing is that it works very fine in another user account but not in the original account.

So pls suggest me some methods to solve this issue

Regards
Vamsee

 

I wouldn't rule out a virus at this stage either...

 

the user account is the administarator which is affected by this so couldnot do anything

 

Is there not a Safe-Mode admin as well?