My mom still has Windows XP which to her is not a problem, but I like building computers and was thinking of maybe building my MOM one for Christmas. She ONLY surfs the web and plays Mahjong, so she needs just a basic computer that's not painfully slow. I just gave her my old 22 inch widescreen Samsung monitor so she doesn't need that. I'm hoping to build somthing for as CHEAP as possible that is 1/2 way descent (not a piece of crap). Windows 7 PC for under $300?
Well, if you put Ubuntu on your new system and give it to you mum, she is going to curse you (trust me, i am a PC user for..11 years now and when i installed Ubuntu 1 month ago on another partition to test it EVERYTHING was upside down...sry got used to Windows )
I recomend http://www.newegg.com/Product/Product.aspx?Item=N82E168...
for web browsing and what ever your mum does
Pretty much your best bet is to get a prebuilt system such as what crisan suggested, since with them you also get the windows 7 license.
However, since you did say that you like building, then i assume it's not _only_ for the benefit of getting get a new computer but also that you get to build it
That will be next to impossible including a win7 license, however you can build one without it for about 300.
Memory: Gskill NS 2x2GB CAS9 1.5V 1333Mhz $25.99
Case: Antec 300 Illusion $44.99 atm with CC generally a decent case in the $30-45 range.
PSU: Antec EarthWatts 380D $39.99
HDD: WD Caviar Blue 500GB $39.99
DVD: Asus/Lite-On/Samsung/Sony DVD writer $18.99 - generally around $20
$320 for the Intel, $334 for the AMD
AMD version costs a few bucks more but probably has a bit more graphics kick and has USB3 and SataIII.
If that's all your mum is doing, I can tell you this will more than suffice for surfing the web, playing Mahjong, other low-end games, even HD video (as long as it's not Silverlight). It also won't hardly use the power of a 40W lightbulb.