My experience - it is NOT worth the effort to attempt upgrading obsolete tech - it consumes more money than simple replacement. Especially when power supplies start to fail (after the first year or so - otherwise replace it - manu defects happen). Power supply failure, imo, is indicative of two things
1.) General component level failure/age that effects the entire machine - so, everything is on its last legs.
2.) Increased current draw by the pc components CAUSING power supply issues - so simple replacement, even upgrade of the power supply - does NOT solve the problem - and in fact, can actually cause a cascade failure. (IE. More current to a failing component simply allows that component to complete its burn down actions.)
Just a quick word on alternates to Dell. Have bought, used, and maintained Dell's in business - they are good machines, but the CONSUMER LEVEL support sucks hind tit. The much more expensive BUSINESS SUPPORT (ie. Server Support Group) are better.
That said - I find Dell to be horribly overpriced.
HP - Hewlett Packard make an excellent line of consumer grade PC's - and they are long lasting also.
The one's that they make for specific distribution from other retailers (such as MicroCenter) locally offer the best bang for buck.
Still have a 7 year old HP desktop that is running quite well. Got an HP ProBook 4530S in February, running Windows 7 - Laptop - and am very pleased with it. Large screen works well for me, 'pro' level offers the 'home premium' edition of the OS (always worth the upgraded cost) - and the built in wireless allows me to use publicly accessible connections. That last part is the sole reason for the Laptop - cut my monthly costs by around 50 bucks by allowing me to get rid of personal ISP. No, it is NOT an ideal way of accessing the internet - but, in current circums, is sensible.
Anyways - Microcenter locally - here's the cost (usually better than NewEgg, whom I do use, but their warranty etc. is problematic at best considering shipping and authorization issues): $400 + ttl.
Excellent buy - good performing, solid Laptop - (yes, a bit heavy - but worth it):
http://www.microcenter.com/single_product_results.phtml?product_id=0388286
I have had good luck and bad luck, both, with generic type PC's that are offered by certain retailers. Some have lasted, others have not. The HP brand has been solid on value for many years for me. Have not gotten zapped by one yet.

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