slow performance after reformatting

[dazednconfuzed]

ok here goes! my cousin got a dell dimension 4600 from her mom. mom says it was working fine then crapped out so it was brought to the shop. shop said to reformat & reinstall windows. the system was failing to boot up completely. well, i reformatted the hard drive, reinstalled windows, & all SEEMED to be well. next day, i went to help cuz install her modem (she is totally pc illiterate). windows is running but VERY, VERY slowly. checked it out & there are two os on the pc. both are windows xp home edition, yet only one will work. dont know what i possibly did wrong. upon startup, the pc always prompts user to push f1 to cont or f2 for setup. this is a new concept for me (its never happened). asked my bro (who is pretty tech savvy just extremely busy) & he said i only should have had to reinstall windows. the old should have been replaced with new. it should have prompted to enter the authentication code & when to insert disks for the drivers......well, it never did. just installed itself & went on about its merry business. i am baffled by this. all the research i have done states that @ least the authentication should have to be re-entered. luckily for me, she has all the original disks that came w/ the pc. i just dont know what to do to remove the other os that isnt working. also confused about why the pc prompts for cmds to be entered before the os will even boot up. if anyone @ all can help me, i would so greatly appreciate it. just trying to help out the fam so she doesnt have to bring it to another shop. oh yeah, dell is no freaking help. why are there two os if i reformatted the hard drive & installed the os all over again????

[Serunson]

Two Questions:
How much RAM has this computer got?
and
How much processing power has it got?
Thanks.

[gerbil]

Jus thow did you reformat the HD? With what tool?