Okay. I went through my setrvices a bit and here are the results. I disabled all the services (which made me unable to connect to internet) and then began enabling them one after one while restarting computer to see if it freezes.

Here is a list of all my services:
1 Alerter
2 Application Layer Gateway Service
3 Application management
4 Windows Audio
Background inteligent Transfer service
Computer Browser
5 C-DillaSrv
Indexing service
ClipBook
COM+ System Application
6 Creative Service for CDROM Access
7 CryptKEy License
Cryptographic Services
DHCP Client
15 Logical Disk Manager
16 Logical Disk Manager Administrative service
DNS Client
20 Error reporting service
21 Event Log
COM+ Event system
Fast USer switching Compatibility
26 Help and support
IMAPI CD-Burning COM Service
Server
Workstation
35 TCP/IP NetBIOS Helper
Messenger
NetMeeting Remote Desktop Sharing
Distributed Transaction Coordinator
25 Windows Installer
29 Network DDE
30 Network DDE DSDM
Net Logon
8 Network connections
Network Location awareness (NLA)
NT LM Security support provider
31 Removable Storage
9 NIVIDIA Driver Helper Service
Plug And Play
IPSEC Services
32 Protected Storage
27 Remote Access Auto connection manager
28 Remote access Connection manager
Remote Desktop Help Screen Manager
22 Remote registry
10 Remote procedure call (RPC) Locator
11 Remote procedure call (RPC)
QoS RSVP
Security Accounts Manager
23 Smart Card Helper
24 Smart Card
17 Task Scheduler
Secondary Logon
System Event Notification
33 Internet connection firewall/Internet connection sharing
Shell Hardware detection
37 Print spooler
12 System restore service
38 SSDP Discovery service
Windows image acquisition (WIA)
MS Software shadow copy provider
34 Preformance Logs and alerts
Telephony
Terminal services
40 Themes
Telnet
13 Trend NT Realtime service
Distributed link tracking service
Upload manager
Universal Plug and Play Device Host
18 Uninterruptible Power supply
Volume shadow copy
19 Windows Time
14 Web Client
Windows Management Instrumentation
39 WMDM PMSP Service
Portable Media Serial Number
Windows management Instrumentation Driver Extensions
36 WMI Preformance Adapter
Automatic Updates
Wireless Zero Configuration

The numbers before the services indicate the enabling sequence. The problem first appeared after I came to and enabled this Theme service + restart. This service makes the taskbar and all the windows look in Win XP Style. I again disabled this service and the problem was gone. Then I tried some more combinations like enabling all the services except the Themes one. And guess what? The problem did not appear. I then disabled all the services except the Themes one and the problem did NOT appear. Weird.

One more discovery is that when I disabled all the non-microsoft services, the problem still appeared. Later I Disabled almost all microsoft services (excluding Themes) and left the non-microsoft services enabled. The problem appeared. And finally, I disabled all the non-microsoft services and left the few microsoft ones enabled. The problem did NOT occur.

Here's a list of the services which I used in the second example - all non-microsoft and few microsoft. Again the numbers indicate the enabling sequence but doesn't make any sence because when the problem appeared the last enabled service was a non-microsoft one... I said before that the problem did occur while all of the non-microsoft services were disabled.


Microsoft:
5 Alerter
6 Application Layer Gateway Service
4 Event Log
1 Remote procedure call (RPC) Locator
2 Remote procedure call (RPC)
3 Themes

Non-microsoft:
7 C-DillaSrv
8 Creative Service for CDROM Access
9 CryptKEy License
10 NIVIDIA Driver Helper Service
11 Trend NT Realtime service


Now what? I'm lost again. Looks like the Themes service is in trouble but I'm sure it's not the causer of the problem because it's a microsoft service and it was running on this PC before the problem arrived.