Your eclipse is 32 or 64 bit ??

How can I find out if a specific Eclipse instance on my (Windows 7) PC is the 32-bit or 64-bit version?

Windows Task Manager Dialog:
Hit ctrl-alt-delete, open up task manager - look at the processes tab. 32-bit programs should be marked with a *32

eclipse.ini file:
plugins/org.eclipse.equinox.launcher.win32.win32.x86_1.1.2.R36x_v20101222

And also you can find in
Eclipse SDK Installation Details:> Configuration page