I was reading your message and what I can tell you is, your problem is in the most causes a Windows Register problem.
Now must you don't bad thinking about that, there is absolute not wrong with your system, but when you download and after that, install programs and then sometimes must you also remove a program, then the Windows Register will be dirty.
Also is it important that you take care that the Volume of your drive is intact, because when the volume has errors then get you also problems.
My advice for you is: First download and install CCleaner, after installation, run that program and select register and then the button analyze, you will see that you get a lot of errors that are in the Windows Register, you will also see when you have ran the tool that there is a button for removing the errors.
When you have do this all, than is it smart that you run chkdsk /p and /r via your system driver, but the possibility is there that you don't have a second partition, in that case, must you to do that via the cmd-box.
When you must to do that, you have 2 possibillities for that: 1. chkdsk /v checkdisk check your system for errors in the system integrity and will try for repair this and you can do this via chkdsk /f/r.
After that, chkdsk check your drive in 5 steps and repair the errors.
Personally check I my drive volume via my repair partition, this partition did I created via msconfig and selected the repair partition and enter, then I rebooted my computer, I got 2 partitions, Windows Xp and the repair partition.
I did also entering more seconds then Windows gives, I did entering also 12 seconds for booting.
I have now more time for making a choice what I will use.
When you have repair the Windows Register and check your volume, I know sure, that you can install the program what you want.
Alright I give you the link for CCleaner.http://www.piriform.com/ccleaner/download