What is the difference between borderlne personality disorder and bipolar disorder (manic depression)?

The two conditions are supposed to be separate, but if you look at a basic oversight of them (i.e. Wikipedia or similar) they seem extremely similar. I was just wondering if anybody with any knowledge about these matters would be able to point out what the differences are between these two conditions.
Thanks in advance for any answers.

Whoops, I obviously slightly mis-spelt 'borderline' in the title there.

Bipolar, or manic depression, is a disorder of mood. The person has mood swings which can be sudden and very forceful. Their behaviour can become quite out of control when they are 'high' because they are elated and thinking very fast. They can suffer extremely severe depressive bouts.
Borderline personality disorder is quite different, although the person may present initially with depression. It is a developmental disorder where the person typically has a poor sense of themselves and their behaviour in relation to other people. They find it difficult to form and sustain relationships because they find it hard to compromise and often have a poor anger management skills. They tend to blame other people for their problems and find it difficult to accept that their own behaviour affects outcomes. So they are often volatile in mood which is where the confusion occurs, but they do not have mood disorder.
Hope that helps.

the biggest difference I'm aware of is that with BPD the patient will suffer with the need to self mutilate: cutting and the like; where as bi-polar patients don't usually cut. With many, if not all mental illness, it is a fine line from one disorder to the next and most disorders are complicated with underling disorders. Diagnosing mental disorders is like a crap shoot, sometimes they get it right but often times they don't.

I havent the slightest idea but my auntie suffers from bipola and my brother has a slight case of it?

Borderline personality disorder is as shown in the film 'Fatal Attraction' where Glenn Close plays a character who has very fragile emotions and builds very unsuitable relationships. You must rent out this film if interested in this condition as she plays an example of this condition excellently. People with Borderline PD struggle to form stable relationships and have problems with attachment that often stem back to childhood. It may be that they had a parent die, leave the family or who was very cold/distant and this is a classic way in which the condition develops. The person never really learns to form proper attachments meaning that they may struggle to understand the feelings of others, they may be volatile or difficult to be with due to their unstable emotions and they may display signs of severe depression however that is not to be confused with BiPolar Disorder (manic depression) which is very different. Borderline PD usually show severe depression when they feel abandonment or may express severe anger when they don't get their own way. They struggle to see the point of view of others and have little empathy. They have emotions which range from severe sadness to extreme rage however their condition is caused and lead by their interactions with others and is a psychological condition as opposted to manic depression which is often an entirely physiochemical condition.

Manic depression is characterised by a constant fluctation between bouts of extreme euphoria followed by bouts of severe, deep depression. This fast turn around of emotions is often due to a physiochemical imbalance in the brain related to dopamine and serotonin, and can be due to low levels of these neurochemicals in the brain or problems with the receptors in the brain to these chemicals. Bipolar Disorder is a type of depression treatable with anti-depressants (which work to correct the chemical imbalance in the brain) and occasionally with electroshock therapy. Counselling therapies are also known to help.

Confusion often comes in terms of treatment between these two conditions, as Borderline PD is also often treated in part with antidepressants however talking therapies are ESSENTIAL in this condition to address the underlying causes and develop better coping strategies and ways of relating to others.

They are different, but they do have one major thing in common - they are both myths created by the drug companies.