Hello, you need to replace the motherboard. This is how I know that its the problem.

1) If it was the memory, it would make beeping nosies but you could still acess the BIOS and etc...

2) If it was the hard drive, you should at least get to the OEM Logo Screen and access the BIOS but everything else will lock up/freeze or just not boot at all...

3) If it was the power supply, the computer would not turn on at all or it would have fried the motherboard if it was the wrong one...

4) If its the motherboard, you will not get nothing at all except for some lights or if you do, you will not be able to do anything and it will shut you down or remain a black screen...

Please contact Toshiba for a replacement if under warranty or to check the price for a replacement.

Toshiba: 1-800-457-7777

Motherboard Replacement

http://www.google.com/products?hl=en&source=hp&q=A205-S4577+motherboard&um=1&ie=UTF-8&ei=32ZOS_G1Lo-1tgf6wdTuDA&sa=X&oi=product_result_group&ct=title&resnum=3&ved=0CB8QrQQwAg

BEST OF LUCK!
GOD BLESS!

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