My father's laptop recently broke - HD failure. It's relatively old and there is no point in fixing it. My question is: Can the screen be unattached and / or reasonably modified to act as a desktop monitor, etc.

In all likelihood, it would be a big pain in the ass:
http://www.geocities.com/p9019/lcdpanel

Thanks for link.

That mod is well beyond my capabilities.

Now its either eBay or trash can.

Often times you can donate old computers (working or not) to schools or other organizations. I would try that as opposed to throwing it away if that was your last option.

If the only problem is hard drive failure, it's easy to just stick in another 2.5" internal hard drive. I just did that for a 5 year old laptop a few weeks ago. So I don't quite get your "there is no point in fixing it comment".. it sounds like this is a working laptop with a failed component, that's all.

I also hope you meant recycle it instead of sending it to the trash can.