Windows 7: Windows changing settings and deleting my files

When I turned on my PC today it ran CHKDSK automatically before loading Windows 7 (I did not not tell it to run). When it was finished, windows loaded up and some of my settings had changed such as mouse speed, desktop backgrounds, cleartext settings etc. Also when I move a window a black outline box appears (see attachment) and I don't know how to fix this.
Can anyone help me out? Also has anyone else had this chkdsk issue?

That's really strange! Had system abruptly turn off sometime - bsod, blackout, etc?!...
I would run a FULL SCAN "offline" antivirus such this one Avira AntiVir Rescue System
After that, I'd install Malwarebytes and should do a full scan too - Malwarebytes
Then, redo setthings as you preferred.

Let us know the results.

"PLEASE REP ANYONE WHO HELPS YOU"

When I switched my PC on today it ran what I think was CHKDSK even though I had never instructed it to do so. The text said something about deleting and retreiving bad files or something. When Windows 7 booted up after, some settings had changed:

• Mouse tracking speed changed
• Personalisation settings changed and saved as 'untitled theme'
• Some changes to windows graphics settings
• 'Cleartext' turned off
• Firefox browser no longer set as default browser
• At least one file (that I have noticed) has been deleted from my hard disk

This seems pretty worrying security-wise. The software I run is Spyware Doctor with Antivirus which has found a few low-risk spywares but nothing major.
Any ideas??

It almost sounds like someone else has taken control. Do you share your computer?

Run Malwarebytes' Anti-Malware:

download Malwarebytes' Anti-Malware to your desktop
|MG| Malwarebytes Anti-Malware 1.46 Download
* Double-click mbam-setup.exe and follow the prompts to install the program.
* At the end, be sure a checkmark is placed next to Update Malwarebytes' Anti-Malware and Launch Malwarebytes' Anti-Malware, then click Finish.
* If an update is found, it will download and install the latest version.
* Once the program has loaded, select Perform full scan, then click Scan.
* When the scan is complete, click OK, then Show Results to view the results.
* Be sure that everything is checked, and click Remove Selected.
* When completed, a log will open in Notepad. Please save it to a convenient location. Copy and Paste that log into your next reply.

No my Pc is not shared. This is the scan result which found a Trojan.Agent.CK
Malwarebytes' Anti-Malware 1.46
Malwarebytes

Database version: 4055

Windows 6.1.7600
Internet Explorer 8.0.7600.16385

30/04/2010 19:18:32
mbam-log-2010-04-30 (19-18-32).txt

Scan type: Full scan (C:\|D:\|E:\|G:\|)
Objects scanned: 369138
Time elapsed: 1 hour(s), 15 minute(s), 14 second(s)

Memory Processes Infected: 0
Memory Modules Infected: 0
Registry Keys Infected: 0
Registry Values Infected: 0
Registry Data Items Infected: 0
Folders Infected: 0
Files Infected: 1

Memory Processes Infected:
(No malicious items detected)

Memory Modules Infected:
(No malicious items detected)

Registry Keys Infected:
(No malicious items detected)

Registry Values Infected:
(No malicious items detected)

Registry Data Items Infected:
(No malicious items detected)

Folders Infected:
(No malicious items detected)

Files Infected:
G:\System Volume Information\_restore{FF6EA0D3-3207-4057-BEB6-DFA8927D7F6B}\RP507\A0157229.exe (Trojan.Agent.CK)

Look at my instructions again ... notice the bolded line:
* Be sure that everything is checked, and click Remove Selected.