How can I deactivate when Acrobat Pro XI wont load?

Question

I installed a purchased upgrade of Acrobat Pro XI on this computer but all I now get is a screen headed 'Sign in Required' inviting me to register my trial version but providing no links to do so.
Much of Acrobat XI Pro did not work.properly but Adobe tells me I don't have sufficient memory despite the required 1GB being installed.
An unsatisfactory product from a company now difficult to contact by email that hides behind an unhelpful 'Help' desk in India staffed by non-proficient English speakers incapable of providing any answers not on their crib sheets.
I am directed here to get a user to do Adobe's work.
What follows indicates Adoobe sens emails from non.valid addresses.
Mail System Error - Returned Mail
From: Mail Administrator <[email protected]>   |   Date: 25/09/2013 3:47 PM  |  Email  
To: John Face<[email protected]>   View message details  
Attachments: Part_0 (350b) (350b)  
        This Message was undeliverable due to the following reason:
Each of the following recipients was rejected by a remote mail server.
The reasons given by the server are included to help you determine why
each recipient was rejected.
Recipient: <[email protected]>
Reason: No such user - psmtp
Please reply to <[email protected]>
if you feel this message to be in error.
Causes nothing but problems.
Just posted on your forums
3:39 PM 25/09/2013
http://forums.adobe.com/post!input.jspa?containerType=14&container=4714
How can I deactivate when Acrobat Pro XI wont load?
I installed a purchased upgrade of Acrobat Pro XI on this computer but all I now get is a screen headed 'Sign in Required' inviting me to register my trial version but providing no links to do so.
Much of Acrobat XI Pro did not work.properly but Adobe tells me I don't have sufficient memory despite the required 1GB being installed.
An unsatisfactory product from a company now difficult to contact by email that hides behind an unhelpful 'Help' desk in India staffed by non-proficient English speakers incapable of providing any answers not on their crib sheets.
I am directed here to get a user to do Adobe's work.
http://forums.adobe.com/thread/1303366
From: Adobe <[email protected]>
To: [email protected];
Subject: Reuse content making tedious work easier
Stop retyping and start reusing.
See how
>>http://www.adobe.com/au/campaigns/acrobat-xi-content-reuse.html?trackingid=KIKZR
Read online
>>http://click.mail.adobesystems.com/?qs=1fdac03698836d3f227a6f8e4faefabc020ad712061d8f58583 a1aeff2e2ddc999d80757db497536
--=----=----=----=----=----=----=----=----=----=----=----=----=----=--
Adobe(R) Adrobat(R) XI
--=----=----=----=----=----=----=----=----=----=----=----=----=----=--
Stop retyping and start reusing. Acrobat XI puts an end to the
busywork when it comes to repurposing PDF file content.
See how
>>http://www.adobe.com/au/campaigns/acrobat-xi-content-reuse.html?trackingid=KIKZS
It?s a breeze to reuse what you need from PDF files with Acrobat XI.
When you need to grab important content from inside a PDF or reuse the
whole thing, Adobe(R) Acrobat(R) XI software makes it easy to convert
PDF documents to Microsoft Word, Excel, and PowerPoint?with no
retyping and minimal reformatting.
As simply as saving a file, you can get just what you need and get
back to more important work.
See how >>
>>http://www.adobe.com/au/campaigns/acrobat-xi-content-reuse.html?trackingid=KIKZT
PC magazine Editor's choice 2012
--=----=----=----=----=----=----=----=----=----=----=----=----=----=--
#Acrobat
>>http://twitter.com/search?q=%23acrobat
--=----=----=----=----=----=----=----=----=----=----=----=----=----=--
PCmag.com Editors' Choice logo is a trademark of Ziff Davis, Inc.
Used under license.
Adobe, the Adobe logo, the Adobe PDF logo, and Acrobat are either
registered trademarks or trademarks of Adobe Systems Incorporated in
the United States and/or other countries. All other trademarks are the
property of their respective owners.
(C) 2013 Adobe Systems Incorporated. All rights reserved.
This is an advertising message from Adobe Systems Pty Ltd, its
affiliates and agents ("Adobe"), Tower 2, Level 27, 201 Sussex Street Sydney,
New South Wales, 2000, Australia.
If you'd prefer not to receive email like this from Adobe in the
future, please click here to unsubscribe. Alternatively, you may
mail your unsubscribe request to:
>> http://click.mail.adobesystems.com/?qs=1fdac03698836d3f1ad59e785d5dc693562fd9325ddedc06b18 2523889dab970e16f0296df7a4a18
UNSUBSCRIBE
>> http://click.mail.adobesystems.com/?qs=1fdac03698836d3f1ad59e785d5dc693562fd9325ddedc06b18 2523889dab970e16f0296df7a4a18
Adobe Systems Pty Ltd
Tower 2, Level 27, 201 Sussex Street
Sydney, New South Wales,
2000,
Australia
Attn:
Field Marketing Department
Your privacy is important to us. Please review Adobe's online Privacy
Policy by clicking www.adobe.com/au/privacy.html (Australia)
>>http://www.adobe.com/au/privacy.html
www.adobe.com/nz/privacy.html (New Zealand)
>>http://www.adobe.com/nz/privacy.html
For customer service issues please visit our web site at
www.adobe.com/go/supportportal or call (AUS) 1 800 614 863 or (NZ) 0
800 485 948 for more information.
>>http://www.adobe.com/go/supportportal
General enquiries about Adobe
communications:[email protected]
>>mailto:[email protected]
If you have a complaint, send it to:[email protected]
>>mailto:[email protected]
This email has been sent to [email protected]
Message was edited by: OQOroger to indicate Adobe uses invalid addresses to customers who have already purchased the subject product

Answer 1

You can refer to :
Acrobat Learn & Support
Installing, uninstalling Acrobat X | Mac OS
Adobe Acrobat X Pro * Activation and registration
http://www.adobe.com/content/dam/Adobe/en/accessibility/products/acrobat/pdfs/acrobat-xi-p ro-accessibility-best-practice…
They are useful resources.
Regards
Rajshree