PC freeze & Modem speed

[DougL]

Whilst surfing the internet my PC has begun freezing from time to time, pressing ctrl-alt del has no effect i.e it will not bring up the administrators box so i can not access task manager, i have to hit the reset button. another problem i have is on occasions whilst trying to connect the modem has a hard time connecting and i then notice that my connection speed can be as low as 4kbs. i can see no conflicts in device manager everything else appears normal, most strange as at other times i can surf the net with no probs.
800 Athlon t-bird
Soyo 75KRV2
W2k
Rockwell sparkle 56K int Modem
Soundblaster 128
ATI Expertpro 2000
256Mb PC 133 SDRAM
20Gig Fujisui H/D