I went to HP's site and looked up your n420a, it's a very old model. You would need to replace almost everything inside the tower with the exception of the drives and, if you have one, graphics card, and maybe the power supply. Once you factor all those in, you would essentially be building a new PC. I'm not sure if you can reuse the case and power supply from the n420a. HP has been known to use proprietary connections. If you really want to go through with a total overhaul of the PC, below are some suggestions.
Motherboard: ASRock M3A785GXH/128M AM3 AMD 785G HDMI ATX AMD Motherboard
- This motherboard allows for AMD's AM3 series processors, DDR3 RAM, and Crossfire. Since you're not a gamer the Crossfire is largely unimportant. However, the board does have on-board graphics so you don't need to purchase a new graphics card if you don't want to. It's pretty weak, but since you're not a gamer, you can live without buying a new graphics card. $94
CPU: AMD Phenom II X2 550 Black Edition Callisto 3.1GHz
- Since you're not gaming, you don't need much more than a dual core CPU. $99
RAM: G.SKILL 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1333
- Plenty of RAM, remember, you need a 64-bit operating system to use 4GB or more of it. $94
Operating System: Microsoft Windows 7 Home Premium 64-bit
- You already said you wanted this. $104
Grand total: $393
Note that you may not be able to reuse the case and power supply, if so add the below on to the price.
Case: COOLER MASTER Centurion 590 RC-590-KKN1-GP Black SECC / ABS ATX Mid Tower Computer Case
- A mid tower case is all you need for a simple build without a gigantic graphics card. If you were a gamer, I would say go for a full ATX case. $64 (Before $15 mail-in rebate)
Power Supply: OCZ Fatal1ty OCZ550FTY 550W
- Plenty of power for now and for future upgrades. $69 (Before $25 mail-in rebate)
Your old PC may use IDE hard drives, those are old and should be replaced with SATA if you have the cash. Also, most hard drives are designed to last for about five years. If your drives are getting old, you may need new ones.
Hard Drive: Western Digital Caviar Green WD5000AADS 500GB 32MB Cache SATA
- Plenty of space for most users. $54
Edited by DJBPace07, 19 December 2009 - 05:23 PM.