Hmm it sounds like your system isn't really healthy eh?
If you can spare the time and have everything you need (drivers, software etc) I'd advice you to completely reinstalll your system. Not the way you reinstalled by installing Windows over Windows, but by formatting your harddrive and starting all over again.
Although your system starts, there seem be to quite some strange things going on, mainly caused by invalid registry entries. You can manually edit your register of course (and some can be down automatically) but the yields won't be that good as when starting all over again.
The one thing you can do to clean your register and hope that invalid entries will be removed/fixed is to make use of the regtool of JV16 Powertools.
About MSOffice: when MSO asks for the CD, try to refer to the location of that file(s) on your harddrive, instead to a CD drive. It might work!
Any program like Excel? Sure, download OpenOffice.org (legal, free and even better in quite some senses ).