System requirements;

:Itel Pentium 4 or AMD Athlon 64 processor.
:Microsoft Windows XP with Service Pack 3; Windows Vista Home Premium, Business
Enterprise or Ultimate or any Windows 7.
:1GB of RAM.
:1GB of available hard-disk space for installation.
:1024x768 display (1280x800 recommended) with qualified hardware-accelerated
OpenGL graphics card, 16-bit color, and 256MB of VRAM
:Some GPU-accelerated features require graphics support for Shader Model 3.0 and
OpenGL 2.0
:QuickTime 7.6.2 software required for multimedia features

To install

1.) De-compress the file
2.) Mount "Photoshop_12_LS1.dmg"
3.) Locate and click on the file "Install" on the image
4.) Select trial serial and install
5.) Quit photoshop if it opens after launch
6.) Open the 'Terminal' application and paste in the following:

sudo /Applications/TextEdit.app/Contents/MacOS/TextEdit /etc/hosts

7.) Enter your password and a text document will pop open
8.) Paste in the following between 127.0.0.1 localhost and 255.255.255.255 broadcasthost

127.0.0.1 activate.adobe.com
127.0.0.1 practivate.adobe.com
127.0.0.1 ereg.adobe.com
127.0.0.1 activate.wip3.adobe.com
127.0.0.1 wip3.adobe.com
127.0.0.1 3dns-3.adobe.com
127.0.0.1 3dns-2.adobe.com
127.0.0.1 adobe-dns.adobe.com
127.0.0.1 adobe-dns-2.adobe.com
127.0.0.1 adobe-dns-3.adobe.com
127.0.0.1 ereg.wip3.adobe.com
127.0.0.1 activate-sea.adobe.com
127.0.0.1 wwis-dubc1-vip60.adobe.com
127.0.0.1 activate-sjc0.adobe.com
127.0.0.1 hl2rcv.adobe.com

9.) Save the hosts document (command+s)
10.) Run the following in terminal to flush your cache:

Sudo dscacheutil -flushcache

11.) Open Photoshop CS5 and click on the help menu and select "Deactivatea?¦"
12.) Select "Deactivate Permanently" then done. Quit photoshop
13.) Reopen Photoshop and enter the serial

1325-0621-9125-0765-3648-0614

14.) Your done