Well I just went through and posted some that are wrong but some that just sound akward, and you should maybe consider re-phrasing. I don't guarantee that all is right here but did my best 
Help file
*smileys should be smilies
*Usergroups should be User Groups (you can argue about that though)
*abbreviation 'for example/that is' eg. should be e.g.
Private Messenger
*'From your Private Messenger you can send and receive Private Messages between yourself and other forum members, knowing that your messages won't be viewed by other forum members.'
Sorry but the whole sentence sounds weird. Try something like
With this Private Messenger you can send and receive Messages to other Forum Members. Messages you send will be viewable only by your recipients.
*Private Messages Overview: Every sentence starts with 'This is' try to change that a little.
*Example:
You have 12 Private Messages, you can receive another 28 out of 40 (delete the out of 40 part or rephrase)
*Messages remain in your Outbox until the recipient deletes the message.
Messages remain in your Outbox until the recipient has deleted the message.
Settings
*Make changes to the information on yourself held in your forum profile
Make changes to the information collected by this forum about you.
Edit Profile
*Indicates required fields
Indicates a required field
*Hide your email address if you want it kept private from other users
Hide your email address if you want it to be kept private from other users
*Sends an email when someone replies to a topic you have posted in. This can be changed whenever you post.
.......whenever you make a post.