Windows System Defender ist nicht mehr zu löschen

ESETSmartInstaller@High as CAB hook log:
OnlineScanner.ocx - registred OK
# version=7
# iexplore.exe=7.00.6000.16915 (vista_gdr.090826-0339)
# OnlineScanner.ocx=1.0.0.6210
# api_version=3.0.2
# EOSSerial=e1e9772c92a46f4ca68c1f98cc3159b6
# end=finished
# remove_checked=true
# archives_checked=true
# unwanted_checked=true
# unsafe_checked=false
# antistealth_checked=true
# utc_time=2009-10-27 06:31:53
# local_time=2009-10-27 07:31:53 (+0100, Westeuropäische Normalzeit)
# country="Germany"
# lang=1033
# osver=5.1.2600 NT Service Pack 3
# compatibility_mode=1024 16777215 100 0 0 0 0 0
# compatibility_mode=8192 67108863 100 0 3739 3739 0 0
# scanned=85305
# found=1
# cleaned=1
# scan_time=3011
C:\WINDOWS\system32\xa.tmp	probably a variant of Win32/TrojanDownloader.Agent.OYU trojan (cleaned by deleting - quarantined)	00000000000000000000000000000000	C
ESETSmartInstaller@High as downloader log:
all ok
# version=7
# iexplore.exe=7.00.6000.16915 (vista_gdr.090826-0339)
# OnlineScanner.ocx=1.0.0.6210
# api_version=3.0.2
# EOSSerial=e1e9772c92a46f4ca68c1f98cc3159b6
# end=finished
# remove_checked=true
# archives_checked=true
# unwanted_checked=true
# unsafe_checked=false
# antistealth_checked=true
# utc_time=2009-11-02 09:46:35
# local_time=2009-11-02 10:46:35 (+0100, Westeuropäische Normalzeit)
# country="Germany"
# lang=1033
# osver=5.1.2600 NT Service Pack 3
# compatibility_mode=512 16777215 100 0 519076 519076 0 0
# compatibility_mode=1024 16777215 100 0 0 0 0 0
# compatibility_mode=1280 16777175 100 0 516586 516586 0 0
# compatibility_mode=8192 67108863 100 0 575241 575241 0 0
# scanned=81947
# found=1
# cleaned=1
# scan_time=4792
C:\Qoobox\Quarantine\C\WINDOWS\system32\drivers\atapi.sys.vir	Win32/Olmarik.OF virus (deleted - quarantined)	00000000000000000000000000000000	C