I have this pc with crt monitor.
lately i have been seeing vertical wave like distortions on the left side and the text looks blurry like a smudge(its very much readable).it was gone when i removed the vga cable and reseated it to the graphic card.but it returns after like 2 or 3 weeks ..is it failing monitor ,vga cable or the gfx card (hd 4650--dvi to vga converter).btw the monitor is samsung syncmaster 798mb plus 17".
I'd guess the monitor. Heat over the life of CRT monitors would usually end their life, sometimes in smoke, sometimes by losing a color and sometimes by just getting blurry. If it was the vid card it would probably return shortly after reseating the adaptor.
you can try 'degauss' option from your monitor's menu. it won't work all the time. or raise the monitor's refresh rate to 75+ hz. the monitor seems very old so you might notice artifacts like this more often.
if you haven't cleaned the display, try cleaning it.