For future reference, you can disable the bluescreen/reboot behaviour to allow you to see the bluescreen properly. Provided you can get to it okay, do the following:
1) Right-click 'My Computer' and choose 'Properties'.
2) Click the 'Advanced' tab.
3) Under the subsection entitled 'Startup and Recovery' click the 'Settings' button.
4) On the separate 'Startup and Recovery' dialog that pops up, untick 'Automatically restart' under the 'System Failure' section.
It's worth saying that, although Windows defrag tools actually use the built-in API to handle the file moving and for that reason are generally very safe, you should *always* check partitions for errors before defragging. Any file system errors present will only be magnified 'x'fold once you start shuffling files around and updating their MFT entries.
In a perfect world the procedure should always be....backup, check and then defrag.
All the best with getting it sorted out.
