Ubuntu: reduce memory consumption - HP ZE5501US with 512 MB

Running Ubuntu 11.04 on my old laptop (although equipped with Pentium 4 and 512 MB of RAM) becomes difficult since the OS is terribly slow. After some analysis it came out that the reason is the 512 MB of RAM (64 MB consumed by the graphic card) which is far too less for the default configuration. Fortunately there is an easy solution to free ~100 MB of additional RAM by disabling the startup applications for gnome environment. You can do it:

1. Ubuntu Classic: System->Preferences->Startup Applications
2. Unity: you can just type 'startup' in the search field

In my case I disabled most of the apps (apart from power manager and few other ones). Below you can see how the window looks like: