problem with read.table

I recently downloaded R on window and running Rgui on NT. I have never use
R before and trying to learn R by following An introduction to R. 
I generated a table of 900x5 in excel and saved as tab delimited txt file.
I then do read.table but I keeping getting the following message

data <- read.table("ML4mm25.txt", header=T, sep=" ")

Error in count.fields(file, sep, quote, skip) : 
  can't open file ML4mm25.txt
and when I try to count.fields, again there is error message. I was able
to use the same command to read the file into S-plus with no problem, can
you tell me what is wrong? also, what is the value for quote?

Hi,
I recently downloaded R on window and running Rgui on NT. I have never use
R before and trying to learn R by following An introduction to R. 
I generated a table of 900x5 in excel and saved as tab delimited txt file.
I then do read.table but I keeping getting the following message

data <- read.table("ML4mm25.txt", header=T, sep=" ")

Error in count.fields(file, sep, quote, skip) : 
  can't open file ML4mm25.txt
and when I try to count.fields, again there is error message. I was able
to use the same command to read the file into S-plus with no problem, can
you tell me what is wrong? also, what is the value for quote?
Thanks.
Chuang Fong Kong, Ph D
Head, Microarrays
Peter MacCallum Cancer Institute - Research
St. Andrew's Place, East Melbourne
Victoria 3002, Australia
Tel: 61 3 9656-1796 or 1138
Fax: 61 3 9656-1411
e-mail: c.kong at pmci.unimelb.edu.au