i want to customize log-in screen

It's in /usr/share/unity-greeter =)

can you give the output of:

lsb_release -a; uname -a; dpkg -l | grep dm

Thanks

I will absolutely provide that data asap. thx

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.1 LTS
Release: 12.04
Codename: precise
 uname -a
Linux JimBuntu 3.2.0-29-generic #46-Ubuntu SMP Fri Jul 27 17:03:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
dpkg -l | grep dm
ii bsdmainutils 8.2.3ubuntu1 collection of more utilities from FreeBSD
ii dmidecode 2.11-4 SMBIOS/DMI table decoder
ii dmsetup 2:1.02.48-4ubuntu7.1 The Linux Kernel Device Mapper userspace library
ii dmz-cursor-theme 0.4.3 Style neutral, scalable cursor theme
ii iptables 1.4.12-1ubuntu4 administration tools for packet filtering and NAT
ii landscape-client-ui-install 12.05-0ubuntu0.12.04 The Landscape administration system client - UI installer
ii libcrypt-passwdmd5-perl 1.3-10 interoperable MD5-based crypt() for perl
ii libdmapsharing-3.0-2 2.9.14-1 DMAP client and server library - runtime
ii liblightdm-gobject-1-0 1.2.1-0ubuntu1.1 LightDM GObject client library
ii libquadmath0 4.6.3-1ubuntu5 GCC Quad-Precision Math Library
ii libwildmidi-config 0.2.3.4-2.1 software MIDI player configuration
ii libwildmidi1 0.2.3.4-2.1 software MIDI player library
ii libxdmcp6 1:1.1.0-4 X11 Display Manager Control Protocol library
ii lightdm 1.2.1-0ubuntu1.1 Display Manager
ii passwd 1:4.1.4.2+svn3283-3ubuntu5 change and administer password and group data
ii policykit-1 0.104-1ubuntu1 framework for managing administrative policies and privileges

Thanks actionparsnip, that solved my question.

Awesome. Thanks. I appreciate the help.