Dale : you can spend all the money you have or you are going to have when your pay comes in , but a decision must be made on your computer system, either you go bare minimals (which I'm thinking your old laptop isn't cutting it thats why you're planning on a desktop) or you can go powerhouse like all the other softies here have stated. believe it or not, personally my own studio PC which I'm using is crappier than the new one stated below. I personally don't believe in getting now, upgrade later, either you get minimal, or you one time gao gao get luxury hehe.
http://fuwell.com.sg/ - my favourite shop ever since they opened at simlim square, under Get Price List
Intel LGA775 CPU + Mainboard Bundle : (on the pdf it's bottom left)
E6700 + Asus P5KPL-AM SE G31 (make sure there's onboard VGA and MUST BE ASUS BRAND!) = $180
Seagate 1TB hdd : $82
Ram (get them to recommend the one which the speed fits with the mainboard, kingston lifetime warranty pls.) : $53+/- 2gb
Andyson Silent G 530W power supply : $75
Coolermaster Casing under $100.
LG Dvd writer $27
because most of the prices I've stated are estimates pluses and minuses, consider getting 4gb ram. (another 2gb) like you don't need 1tb hdd, go for 500gb, then contribute into the ram, or got old dvd writer, ditch it etc. if you still have your old computer's OS cd then you can save on that.
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my recording laptop (for 8 tracks drums) : 1.66ghz Core2Duo, 2gb ram. 5400rpm hdd.
my mixing DAW desktop : 2.4ghz Core2Duo E6600 , 2gb ram , 7200rpm normal SATA hdd. but hdd space I got about 7TB
windows xp 32bit OS.
problems? nope, secret behind shit specs? a very good habit of maintenance. defrag,backup, no games nonsense etc.
what senn_liu has said bout the noise from CPU is very true except I use a very simple method of : go into BIOS/CMOS setup, under hardware/fans, set to ultra silent mode (a.k.a slow down the speed of the fans) , although your hdd will get warmer than usual, but hey if you're only recording vocals on a sensitive condenser, it's 1 track better than 8-16 tracks dynamics (overheads condenser) mics which aren't going to pick up much from your cpu. have your aircon remote beside you, turn off before recording. done. when you're mixing, better remember set the fans to performance mode.