Suggestions and help about buying ram,harddisk,ups

hi to one and all

i already have ---

512mb dynet ram 2.67ghz
80 gb hitachi SATA harddisk
microtek ups which does not even give 1 sec backup and have been using this since 2 years.

so,
tomorrow or day after tomorrow i going to buy ram,harddisk and ups

i stay at hyderabad and it would be great help if anyone guides me to a good shop at ctc secunderabad.

I am thinking of buying 1gb dynet ram which costs Rs.1050 and ups of mercury or beetel of around Rs 1200

still cant decide about harddisk...............


Please advice as I am confused as my knowledge is very puny.


Thanks in advance.