You would need to upgrade ram/MB/CPU/ + probably video card and case (the 166 came out at the end of the AT beginning of ATX case area so you'd probaly need a case.
Case w 300W P/S = $45
ECS MB = 55 (built in sound & LAN)
AMD XP1700 = 65
256MB DDR 2100 = 50
32 MB TNT2 Video = 50
That's using you'r old drive (probably very slow & low capacity)
40MB 7200RPM ATA100/133 = 80
CDRW = 50
That's an OK rig with OK but barebone parts.
Add $85 for the OS...
*** All those prices were off the top of my head, likely a little cheaper ***
Computer show @ CCRI this weekend
http://www.gateway.com/home/prod/hm_...oddetail.shtml
Processor Intel® Celeron® Processor 2.1GHz with 128K Cache compare
Memory 128MB DDR SDRAM
Storage40GB UATA100 5400RPM Hard Drive
Media Drives3.5" 1.44MB diskette drive
48x/24x/48x CDRW (Limited Time Promotion)
Graphics Integrated Intel® Extreme Graphics with up to 64MB Dynamic Video Memory
Audio & Speakers Integrated Enhanced Audio GCS300™ Speakers
$533 after rebates - not any faster than the above parts...
No OS - but I could get you a decent mid range PC for $200