When my girlfriend visits me, she has to work on a mini PC while I use my laptop to finish whatever I postponed at the office. Her PC has a 1GHz VIA processor and 128 MB of RAM and runs Ubuntu. You can imagine how slowly it boots, even with Linux installed, and GNOME runs so slowly that it's quite irritating. I didn't want to reformat and install a lightweight Linux distribution like Fluxbuntu because the mini PC doesn't have a CD-ROM drive, and I already had 10GB of data that would have taken a long time to back up. Instead, I found and installed some lightweight software to improve her computing experience.
The problem with speeding up your desktop is that you have to make certain usability compromises. I had to make my girlfriend's desktop fast, yet as user-friendly as the GNOME environment she uses on her own Ubuntu-based computer at home.
I installed iDesk to give her icons on the desktop on top of the Fluxbox desktop environment. The icons are defined through .lnk files located in ~/.idesktop for each application you want to appear on the desktop. For example, to create a shortcut to Firefox, you would create a file with
touch ~/.idesktop/firefox.lnk with the following contents: