Swifty - you do not need to CRASH the computer - you may wish to reinstall the operating system but you don't need to CRASH it... Given that you have no recovery disk you are best off fixing the problem.
This from the Microsoft site
1. Open Windows Defender by clicking the Start button Picture of the Start button, clicking All Programs, and then clicking Windows Defender.
2. Click the Tools button, and then click Software Explorer.
3. In the Category box, click Startup Programs.
4. Select the program that you want to prevent from running, and then click Disable.
5. Click Yes to confirm that you want to stop that program from running.
6. Repeat steps 4 and 5 for every program you want stop from running.
Peccavi, December 2008