This trojan blocker ( MD5: f2e9fdb9db823a412b5f3cc63c9a2a25 ) prevents all software execution.
To remove the Trojan (and unlock windows), infected users need to enter a valid serial number.
According to VirusTotal this sample is detected by just 4 Antivirus: http://www.virustotal.com/file-scan/report.html?id=e93a4cd81b3a7f0e1c424996451b456c470b7d92d703cd285617a502d4c29b86-1302690666
Unpacked version (UPX + Crypter + UPX) is detected by 9 Antivirus.
Unfortunately, unlock code are not stored inside the binary, there is no way to get it with reverse engineering.
1) Restart your pc
2) Before the Windows XP splash screen, press the F8 key to enter the Windows Advanced Options Menu and choose: Safe Mode With Command Prompt
3) Type 'regedit' in the console and go here:
4) Find the key 'Shell' and replace the value by 'explorer.exe'
5) Reboot your pc.