Many lags with my Desktop

Many lags with my Desktop

I have this problem for over 3 months now.My desktop computer after some
hours it gets some lags like some 3-5'' and then runs smoothly about a
minute or two and then again lags e.t.c..This issue doesn't happen always
for example it might pass a day by and this doesn't show up.Also seconds
before the lag the cursor becomes some kind of a narrow and yellowish.Any
clues please help , have someone else had the same problem .
specs (windows7 x64 ultimate, i5 with 1156 socket with an asus
motherboard,gts 450 gigabyte graphics card)
Furthermore it must be on the hardware the issue cause I reinstalled
windows .