Sajid,
Are you behind firewall / proxy? Have you verified the downloaded installer file size and md5sum matches that mentioned in the download site? I think your office network might be prohibiting you from installing, can you verify the same with your networks department.
Mentioned below are alternate ways to install MyEclipse –
a) Install using update site
To Install Using Eclipse Update Site: be sure Eclipse 3.5.2 “Classic” is installed.
Start Eclipse > Select Help > Software Updates > Available Software Tab > Add Site > Enter this URL
http://downloads.myeclipseide.com/downloads/products/eworkbench/galileo/enterprise-stable
From there you just “Next” your way through the wizard and MyEclipse will be installed for you.
b) Install using archived update site
Please refer https://www.genuitec.com/forums/topic/installation-install-myeclipse-using-archived-update-site/&highlight=&sid=dd2edb79b7e410ce1c055cd6bfd54ec5
c) Install using pulse
1. Open Pulse. If you don’t have pulse, download from http://www.poweredbypulse.com
2. Login to pulse. You can also login anonymously
3. Select “Eclipse – Galileo” realm from top left hand corner dropdown
4. Expand and click on – Ready to use Profiles > Popular
5. From the right hand pane, right click on “MyEclipse 8.5” and click on [run]
6. This will open a wizard which will guide you through the rest of the steps.
Let me know how this works for you.