@ SafeSurf
I did a quck and full scans of Disc C with Avast and it found no threats. However, MBAM did:
Malwarebytes Anti-Malware (Trial) 1.62.0.1300
www.malwarebytes.orgDatabase version: v2012.07.31.07
Windows XP Service Pack 3 x86 FAT32
Internet Explorer 7.0.5730.13
Администратор :: COMPUTER [administrator]
Protection: Enabled
31.07.2012 14:05:04
mbam-log-2012-07-31 (14-05-04).txt
Scan type: Quick scan
Scan options enabled: Memory | Startup | Registry | File System | Heuristics/Extra | Heuristics/Shuriken | PUP | PUM
Scan options disabled: P2P
Objects scanned: 185498
Time elapsed: 4 minute(s), 1 second(s)
Memory Processes Detected: 0
(No malicious items detected)
Memory Modules Detected: 0
(No malicious items detected)
Registry Keys Detected: 1
HKCR\CLSID\{665C94CF-F293-11D1-B2E4-0060975B8649} (Trojan.Ardamax) -> Quarantined and deleted successfully.Registry Values Detected: 0
(No malicious items detected)
Registry Data Items Detected: 3
HKLM\SOFTWARE\Microsoft\Security Center|AntiVirusDisableNotify (PUM.Disabled.SecurityCenter) -> Bad: (1) Good: (0) -> Quarantined and repaired successfully.
HKLM\SOFTWARE\Microsoft\Security Center|FirewallDisableNotify (PUM.Disabled.SecurityCenter) -> Bad: (1) Good: (0) -> Quarantined and repaired successfully.
HKLM\SOFTWARE\Microsoft\Security Center|UpdatesDisableNotify (PUM.Disabled.SecurityCenter) -> Bad: (1) Good: (0) -> Quarantined and repaired successfully.Folders Detected: 0
(No malicious items detected)
Files Detected: 0
(No malicious items detected)
(end)
Frankly, I dnn't think that these may be the cause of the problem since after MBAM had deleted them and I had repaired avast again nothing changed.