PC booting only after repeated attempts. Pls help this poor kid.

[Harshilvijay]

Hii.
OK so my PC is around 5 Y/O here are its specs-
Dual core E5700
4 GB DDR3
HD 6670 DDR5
450w PSU.
So around one month ago, I noticed that I had to start the PC twice to make it boot. I mean all the fans and things are just OK but the PC won't boot. But nowadays it takes more than 10-15 attempts to make it boot.
I searched on internet , I found out about the Beep sound motherboard thing, but there is no beep sound made by my motherboard even when I remove the RAM/GPU , etc and then run the PC.
Also I've tried clearing the CMOS battery ,but it didn't help either.
Also my PC is very slow nowadays, It takes 30-60 seconds to even open a single program, VLC is freezing Everytime I play any video on it.Earlier I could edit videos with ease but from past days even the video editor is lagging and freezing. But surprisingly I could play games without any problems( Far cry 3 @ High/Medium).

Both the problems have occured simultaneously.
Please help me and tell me what's wrong. As I'm an 18 Y/O student, I can't afford a new motherboard ,etc and I'm preparing for an exam so I have to regularly take tests through the PC.
Please help.

 

[Paul NZ]

May need a defrag or a new hdd

 

[Harshilvijay]

I've already defeated all the drives yesterday to no avail.

 

[Ravi Sankar]

Dismantle your PC and clean each and every component in petrol and assemble it back, it should work

if possible, change the MOBO to HDD cables (both data & power cables)