Computer Won't Start Up...

I had a very bad day yesterday. Unfortunately, this unluckiness also rubbed off onto my computer, and now my PC won't start up. I've had this problem before, but after I shut down the computer and then restarted it, the problem was gone and it started up fine. Basically, this is what happens:

I start up my computer and everything works fine. It does the memory check and the memory check is OK. But then when it attempts to detect my hard drives and CD-drives, nothing gets detected. It says "SATA1_NONE" and "SATA2_NONE" for primary master and slave, and then it just says "None" for secondary master and slave. Obviously with my hard drives not being detected, my OS doesn't load and the computer doesn't start up.

I recently added a new 250GB hard drive, and my power supply is only a stock 250W or 300W (not sure exactly which one, but it's somewhere in that low, low range). I have a feeling that it's my power supply that's causing the problem, but even after unplugging the 250GB hard drive, the problem still persists... Does anyone know what the problem could be? Also, I'm quite short on cash so if anyone has any temporary fix until I get the money to replace whatever hardware needs replacing, that would be the ideal solution.

Thanks for any help in advance.

 

First of all, disconnect all drive(s), except the one with your operating system on, IF YOU HAVE OTHER DRIVE(S) SET IN THEIR OWN DRIVE LETTER.
If it will not start then, it could well be the power supply. If it does start, it could still be the power supply, possibly failing, as it is a bit puny, to say the least.
If you have 2 sata drives, and a dvd writer, you are pulling a lot of power off the main rail.
Have you done your system cleanup - disconnect from power lead, and when cold, use an aerosol air cleanig spray to blow out dust, and fluff.

You have not given any specs on your machine (motherboard, graphics , programs, ram, or, cpu. These could help to determine your psu needs- but I suggest , as PSU is a very cheap component, you purchase at least 450 watt, for todays computing.

 

I actually had disconnected all the drives except the one with the OS last night and it didn't work, but I tried it again today and it's fine. So then I reconnected my storage hard drive (since literally all my files are on that) and it's working right now. I don't know how long it will be until it screws up again, but I'll be looking into a new power supply soon.

As far as system specs go, they are as follows:

Gigabyte 865PE Motherboard
Intel P4 2.4GHz processor
2x512MB Kingston PC3200 ValueRAM
128MB Powercolor Radeon 9600 Pro
250GB HDD
80GB HDD
DVD R/RW Dual RW Drive
CD-RW Drive

 

It is worthchecking if ram has not 'lost contact', dust/fluff. You can try removing and relacing, as this sometimes solves that side, or download memtest86 from majorgeeks, and run it for 4 passes to check it.
Have you got Everest 220 ?(again available, and free download from majorgeeks) This can give you temperatures (in case of overheating) and rep[ort most of system situation.
Are the cpu, and psu fans working/ not loaded with fluff?
Unfortunately, I am off ' now, but report your answers, and there are many around to help, if you follow the suggestions.