Opening Windows Office 2003 files

[pacpalm]

I run XP Home SP2 with Office 2003.
Of late, Word, Excel and Powerpoint files take an exceedingly long time to open.
What usually happens is that I click on the file link in a directory and must wait between 15-20 seconds before the Word, Excel or PP blank starter page opens. Then another 15 seconds or more goes by before the actual file opens. Thus, total time to open a file can approach 25-30 seconds at its worst.
I regularly use "cleaners" to remove useless files from my hard drive. I have no viruses that I know of, since I regularly use spyware and antivirus programs, as well. I also have tried to shut down unnecessary programs running in the background.
Why would my Office files open up so slowly?

Thank you.