Frequently having to Ctrl+Alt+Del and End Now programs

My computer often locks up 1 program (when I'm using several, but will only lock 1 out of the group) and I have to end it through Ctrl+Alt+Del (I often have to try to end it 2-3 times before it'll actual end it). I will open that program a few seconds later and it will freeze it again after a few minutes. My computer likes to do this most to IrfanView.
Over the past week or so I have also been having lots of issues with Microsoft Office. Anytime I open a Word doc it takes a very long time to open up and then it opens in 2 tabs on my task bar and one of them is blank and when I exit out of the blank one it pops up a lot of things about a "Normal" file. Excel also takes a very long time to come up.
Also, I am not sure if this is related (and it doesn't really bother me, as I use Firefox, and it has been happening for over a year now) but anytime I open IE it freezes everything and I have to manually shut off my computer.

 

Microsoft Office seems to be behaving better, but the photo-viewing program still crashes fairly often. Also, my computer seems to now be slower to open Firefox and it's running at 90-100% almost constantly, which it was not doing before.