I found a file twitter.exe in my picture folder.

My twitter account was suspended they said my account was compromised. but i had been on twitter most of that day. so when I noticed this file I clicked on the properties and it said it was an MSDOS.exe and it said it was set to execute on restart. I contacted twitter support and they wanted me to send them the file attach it in the email. well I tried that but google blocked it it said I can not send an exe file, because it could attack the receiver when they open it. or attack the google system. Then my gmail account was suspended. but twitter and I both talked to google and they lifted the suspension. I scanned just that file with McAfee security and it came back with unknown file type. and said: let McAfee know about this program, it had a report button i clicked report. next thing i notice my computer is acting strangly when i open a program the window is black for a few seconds then i get the program, but the programs I'm using keep closing on me. then I clicked on the Firefox icon to connect to the internet and it said firefox in not installed or it has been moved or changed. so I clicked on Internet explorer. it would not open at all there was no message. so I reinstalled firefox it worked. but it too kept closing. then i got a message from McAfee saying it got a critical update and needs to restart the computer. I thought about what that file said set to execute on restart. then the computer shut down. when it restarted it McAfee started a full system scan and it quarantined that file and another file called twitter.dods it reported them then shredded them. but now my computer is running really slow and the cpu is running at 95 to 100% when idle and nothing open. I looked in the program files and every file on my computer is doubled. there is two of everything. even registry keys and sub files and os files everything. how do i get rid of all the doubled files? I am running my computer in safe mode at the advice of McAfee and my AT&T they both told me to come to this site because they have never heard of anything like this before. they both went remote on my computer to verify this has really happened. they say if anybody can answer this question it will be answered here.
So if anyone can tell me how to get rid on all the doubled files on my computer please tell me.

PS: I was told to post this under Twitter, and Microsoft both.