BleepingComputer.com: Computer Still Freezes Randomly

Ever since I replaced the CMOS battery, my computer keeps freezing randomly and I am forced to soft boot it to get back in. Some common features that I notice are:

1) Taskmanager usually shows 100% CPU utilisation (though at times it freezes even at 88%)
2) ALWAYS freezes when I'm using skype (even without video) after about 2-10 minutes of OK usage
3) Freezes quite often on specific webpages which have flash videos or fancy graphics, even though I haven't started the video
4) Upon rebooting, freezes sometimes even when I haven't opened any application
5) Always freezes when I do a deep spyware scan using HouseCall or Spyware Terminator, even when in Safe Mode. A standard quick scan shows no problems. I use Avast Antivirus which ran the deep scan properly and found no problems. Installing Office 2007 also froze the computer during installation.

Temperatures:
Motherboard 21 °C (70 °F)
CPU 27 °C (81 °F)
GPU 40 °C (104 °F)
GPU Ambient 30 °C (86 °F)
Seagate ST3250823AS 33 °C (91 °F)
DW CDW63G0-D00NF0A 32 °C (90 °F)

Process PID CPU Private Bytes Working Set Description Company Name
System Idle Process 0 96.08 0 K 16 K
Interrupts n/a 0.98 0 K 0 K Hardware Interrupts
DPCs n/a 0 K 0 K Deferred Procedure Calls
System 4 0 K 88 K
smss.exe 428 176 K 64 K Windows NT Session Manager Microsoft Corporation
csrss.exe 652 1,564 K 2,060 K Client Server Runtime Process Microsoft Corporation
winlogon.exe 676 7,872 K 1,284 K Windows NT Logon Application Microsoft Corporation
services.exe 720 0.98 1,840 K 1,880 K Services and Controller app Microsoft Corporation
svchost.exe 888 3,080 K 1,848 K Generic Host Process for Win32 Services Microsoft Corporation
svchost.exe 984 1,868 K 1,880 K Generic Host Process for Win32 Services Microsoft Corporation
svchost.exe 1100 13,876 K 14,688 K Generic Host Process for Win32 Services Microsoft Corporation
svchost.exe 1196 1,724 K 1,904 K Generic Host Process for Win32 Services Microsoft Corporation
svchost.exe 1328 1,628 K 1,696 K Generic Host Process for Win32 Services Microsoft Corporation
AvastSvc.exe 1560 14,120 K 28,632 K avast! Service AVAST Software
spoolsv.exe 300 3,948 K 1,772 K Spooler SubSystem App Microsoft Corporation
svchost.exe 1288 1,404 K 1,284 K Generic Host Process for Win32 Services Microsoft Corporation
jqs.exe 1340 2,364 K 1,396 K Java™ Quick Starter Service Sun Microsystems, Inc.
svchost.exe 1668 2,632 K 2,216 K Generic Host Process for Win32 Services Microsoft Corporation
alg.exe 2452 1,264 K 1,036 K Application Layer Gateway Service Microsoft Corporation
lsass.exe 732 3,848 K 540 K LSA Shell (Export Version) Microsoft Corporation
explorer.exe 1492 0.98 27,384 K 20,740 K Windows Explorer Microsoft Corporation
ctfmon.exe 1568 1,132 K 864 K CTF Loader Microsoft Corporation
AvastUI.exe 1732 5,988 K 6,420 K avast! Antivirus AVAST Software
CDAuto.exe 1752 2,224 K 908 K
soundman.exe 1760 2,132 K 1,656 K Realtek Sound Manager Realtek Semiconductor Corp.
Skype.exe 1768 26,248 K 18,928 K Skype Skype Technologies S.A.
skypePM.exe 608 16,280 K 4,796 K Skype Extras Manager Skype Technologies
firefox.exe 1640 151,612 K 146,724 K Firefox Mozilla Corporation
plugin-container.exe 232 18,084 K 11,556 K Plugin Container for Firefox Mozilla Corporation
explorer.exe 2968 14,260 K 21,824 K Windows Explorer Microsoft Corporation
WINZIP32.EXE 1368 3,088 K 7,584 K WinZip Executable Nico Mak Computing, Inc.
procexp.exe 1748 0.98 8,648 K 13,800 K Sysinternals Process Explorer Sysinternals - www.sysinternals.com

Sensor Properties:
Sensor Type HDD

Temperatures:
CPU 21 °C (70 °F)
Seagate ST380215A 50 °C (122 °F)

PF Usage: 340 MB
Physical Memory (K): Total 515568; Available 148692; System Cache 140000

The tower is in a pigeonhole cabinet