Computer runs very very slowly when I run Ms Office 2007

Are you even running ubuntu? If so, you must be using wine to do so, as word is not a native application.

If you have zero swap usage, then expanding the drive is not going to make anything faster. swapping is only a problem when you start to run out of ram. At 25% usage, you are not going to have a major problem there.

I'm sure you have a reason to be running office, but did you try using libreoffice instead? As a proper native application, it will -instruction for instruction- be significantly faster than something running under wine, as there is no need for translation between windows and unix system calls,

http://appdb.winehq.org/objectManager.php?sClass=version&iId=4992

Wine is not incredibly frugal with resources. Have you tried Libreoffice....

Ya, I use WINE.
I use Ms Office because my lecturers give handout in a softcopy in pptx format, which is can only be opened in ms powerpoint 2007 or later. I try to open pptx using openoffice (as i choose ubuntu 10.10 as my OS despite the latest version, ubuntu 11), but openoffice cant read the presentation.

I admitted, ubuntu is so far more advanced in interface than windows, even MAC..but its only office application that not well used.

With LibreOffice 3.4.4, I was able to read in and display a pptx format file. https://wiki.ubuntu.com/LibreOffice describes the installation process for LibreOffice. It requires that you uninstall OpenOffice first.

This does not guarantee that LibreOffice is a good solution. Your document may use MS Office features that OpenOffice and LibreOffice do not handle correctly.

System->Administration->Monitor : what is swap disk usage reported ?
Could you also provide partition table: sudo fdisk -l

Libreoffice is not the only office app, there is Abiword and Gnumeric which can perform word processing and spreadsheeting respectively.