Upgrade woo-hoos to Upgrade blues. Help!

[mightyboosh]

Hello,
I'm at the end of my rope and hanging by my teeth; writing this hoping that someone out there will help me.

About a month ago, my HDD crashed and i thought of 'upgrading' my RAM (Big mistake) since i was getting a new HDD anyway.

The following are some of the tortures i had to endure which has prompted me to write to you all;

Well, okay i got the new HDD and the new RAM, but my computer never started. so i go back to him with the cabinet (since i couldn't find the OS anywhere)

I get it back; i go to my room all excited about my 'new' computer and every program i start on it is crashing; i go to him again with my cabinet. Turns out that my RAM was not compatable (or something like that)

Then when i finally got it back; the Computer wouldn't start at all; yep i had to take it back and this time i had to put in some more money to put a new SMPS.

I got my computer back from him a few days ago; and after about an hour of it working; the monitor just stut off and the computer wouldn't start.

I go to him YET AGAIN, and got it back a 3 days ago; now the computer takes about 5 minutes to start up (sometimes it just freezes halfway through and i have to restart) (also keep in mind that i have a 512 MB ram so it shouldn't take more than 2 minutes to start)
so i opened up the side panel and realised that he had also changed the RAM on my CPU (he said the previous one was giving him trouble)


After it starts, any program that i start on it crashes after some time. Say if i'm writing this thread on Firefox, it will crash in some time with an error sign, if i open internet explorer, it'll crash almost immediately, if i run more than one program at a time it will crash. What i want to know is that is this all because of faulty RAM or because of some glitch on the motherboard.

Another problem that recently came up even after changing the SMPS is that i have to press the button four or five times before the CPU starts..

If you read the above thread and know what i'm going through right now; i would request you to advice me about what i should do. I know i shouldn't have trusted just anyone and i wouldn't give him my cabinet if i can help it; but if it's faulty RAM then i just have to interact with him again, don't i?

Please give your valued suggestion (along with a smack on my head for being stupid)
__________
EDIT:

I also wanted to ask; How do i figure out if my RAM's compatible with the mother board..

[sinstoic]

Originally Posted by mushroomcloudwarrior

...Another problem that recently came up even after changing the SMPS is that i have to press the button four or five times before the CPU starts...

If you have a graphics card that goes into PCI, AGP of PCIE, ensure that it is plugged in properly and any loose-contacts are ruled out!

Sort out memory issues by checking your memory in another similarly configured computer.