Windows 7: something's up with my PC

Download & install Malwarebytes Antimalware, update it, then do a full scan.
If it wont install or update, boot to safe mode with networking & do it there.

No problem, post back if it solves your problems, or you have any issues or questions.

Scan type: Flash scan
Objects scanned: 136065
Time elapsed: 27 second(s)

Memory Processes Infected: 0
Memory Modules Infected: 0
Registry Keys Infected: 3
Registry Values Infected: 0
Registry Data Items Infected: 0
Folders Infected: 0
Files Infected: 2

Memory Processes Infected:
(No malicious items detected)

Memory Modules Infected:
(No malicious items detected)

Registry Keys Infected:
HKEY_CURRENT_USER\SOFTWARE\8DDYX0ZBPZ (Trojan.FakeAlert.SA) -> Quarantined and deleted successfully.
HKEY_CURRENT_USER\SOFTWARE\XMZH42I4GI (Trojan.FakeAlert.SA) -> Quarantined and deleted successfully.
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\ (Hijack.Zones) -> Quarantined and deleted successfully.

Registry Values Infected:
(No malicious items detected)

Registry Data Items Infected:
(No malicious items detected)

Folders Infected:
(No malicious items detected)

Files Infected:
c:\Windows\Tasks\{22116563-108c-42c0-a7ce-60161b75e508}.job (Trojan.Downloader) -> Quarantined and deleted successfully.
c:\Windows\Tasks\{810401e2-dde0-454e-b0e2-aa89c9e5967c}.job (Trojan.FraudPack) -> Quarantined and deleted successfully.

Do you think these are the reasons for above symptoms ?.. Do I need to do some other things? Any way thank you for helping...

Those could have been the source of the problems. Have you tried running the tools that didn't work before, since the MBAM scan?
I recommend that you download SUPERAntiSpyware free, install & update it, then do a full scan.
I have both MalwareBytes & SUPERAntiSpyware installed on my system(in addition to my AV) as on-demand scanners & they haven't failed me yet.
Also scan with your resident AntiVirus, you can never be too careful when it comes to malware.

I have both MalwareBytes & SUPERAntiSpyware installed on my system(in addition to my AV) as on-demand scanners & they haven't failed me yet.
Also scan with your resident AntiVirus, you can never be too careful when it comes to malware.

he recent scene is when I try to run Windows Defender it shows the window just for a second and disappear.. then I downloaded the Microsoft Windows Malicious Software Removal Tool ,when I double click on it, it shows self extracting but doesn't run.. no error reports and nothing just not running..